Field of the Invention The present invention relates to remote-access apparatuses, especially to methods, devices, systems and computer programs for calibrating remote-access apparatuses for measurement purposes and storing data, especially a part of a calibration database, on a remote-access apparatus and the remote-access apparatuses with such functionality.

Background of the Invention

Modern logistics was to a great degree enabled by the development of the product code system and bar codes. Products and pallets could be quickly identified by reading a bar code with an optical reader, and the tracking of items in the logistic chain became feasible. Furthermore, the products could be counted and sold at the point of sale more quickly and more reliably. Beyond consumer product logistics, industrial material management systems, postal and courier services, healthcare and bio-analytics systems and many other fields of human activity have benefitted from the use of bar codes.

Over time, the needs of having various kinds of information available on a product outgrew the capabilities of a simple bar code. To this end, new technologies were developed, such as two-dimensional bar codes. Of such tech- nologies, radio frequency identification (RFID) has rather quickly become the technology of choice for identifying and tracking items. RFID technology has a vast number of applications making use of the ability to read an RFID tag from a distance even without a line-of-sight connection between the reader and the tag. RFID is quickly replacing or at least augmenting the bar code technology in many places.

The basic information that an RFID tag carried has traditionally been electronic product code (EPC) information and/or tag identification information. RFID tags with more capabilities may have the ability to store more informa- tion in the tag memory, and even carry out some simpler processing of data. A radio frequency identification tag (RFID tag) typically comprises an RFID chip and an antenna connected to the chip, attached to or protected inside a plastic layer. The RFID chip contains analog and/or digital processing circuitry, e.g. a state machine and/or a processor and memory for storing informa- tion, as well as circuitry for receiving radio frequency (RF) energy and modulating the RF wave. The chip is connected to the antenna, whose shape and size depend on the frequency at which the tag operates and the application for which the tag is used. The chip and the antenna are often laid inside a thin plastic container for protection. The tag as a whole is typically flexible to a certain degree, especially the passive tags that do not contain a power supply.

Passive tags use the energy from the radio-frequency electromagnetic field of the read-out signal to power the operations that the tag carries out. Pas- sive tags operate essentially while they are in the reader field, and are essentially inactive at other times. Therefore, the farther the reader device and the weaker the read-out signal, the less energy is available for the tag to use. This in turn means that the tag cannot perform very complex operations that would require a lot of power, since such tags could only be read from a very short distance away. In other words, the read-out distance of a tag is to a large extent determined by the power consumption requirements of the tag. Naturally, the attenuation and power distribution of the electromagnetic signal emitted by the tag is another concern. To tackle this issue, some passive tags have a battery that may be used to power the processing circuitry and thereby allow longer operating range for the tag. Such tags that use an internal power source to energize the response signal may be called semi-passive tags.

Some applications may necessitate more complex processing and/or more demanding properties of the RFID tag. It may become necessary to arrange more internal power such that these operations may be carried out. Some tags may require an internal power source to communicate with a longer range. Such tags may be called active tags. It may also be necessary to provide internal power so that operations can be carried out at times when the power from the external radio frequency electromagnetic field is not available. Usually this is arranged by means of a battery attached to the RFID tag. The battery may power sensors, memory, processors and/or a transmitter of the tag so that sensing, data logging and processing may be carried out at any time. Such more complex tags may be more complicated to manufacture, more expensive and/or more prone to malfunction than passive or semi- passive tags. Moreover, any tags with an internal power supply may have a limited lifetime, since they cannot be operated properly or at all when the battery runs out. Another practical problem is that when an active tag is taken into use, the battery operation needs to be activated. Otherwise, the battery would be in use e.g. already starting from manufacturing of the tag and prior to actual active use.

An example of demanding properties of a tag are measurements. In some applications, wireless measurements regarding the environment may help process or quality control. Active tags are often larger and more expensive than passive tags. Furthermore, in some applications, particularly related to construction engineering, the battery of the active tag may be difficult to change. Therefore, e.g. for process or quality control, passive tags capable of measurements are needed. Such tags may need to be calibrated for better measurement accuracy.

In order to carry out more complex operations with a tag, there may be a need to store more data on a tag. In addition, some of the data may need to be protected from unauthorized access. These requirements make the tag more complicated, and possibly make the tag consume more energy. This, in turn, has the drawbacks mentioned above.

There is, therefore, a need for solutions that facilitate the use of simpler tags for more complicated operations. Summary of the Invention

Now there has been invented an improved method and technical equipment implementing the method, by which the above problems are alleviated and that enable the use of simpler remote-access devices for more complex ope- rations than before. Various aspects of the invention include methods, reader apparatuses, a systems, a remote-access devices and computer readable media comprising computer programs stored therein for carrying out the methods and operating the devices, which aspects are characterized by what is stated in the independent claims. Various embodiments of the invention are disclosed in the dependent claims.

Description of the Drawings

In the following, various embodiments of the invention will be described in more detail with reference to the appended drawings, in which

Figs. 1 a and 1 b

show block diagrams of an RFID tag and a reader device, respectively;

Figs. 2a and 2b

show methods for reading data from a remote-access device according to an example embodiment; Figs. 3a and 3b

show methods for writing data to a remote-access device according to an example embodiment;

Figs. 4a and 4b

show tags with application data stored in a password area, and with application data stored in a password area and protected by an access key;

Fig. 5 shows a memory configuration of a tag according to an example embodiment;

Fig. 6 shows a method for deriving application data from a password memory of a tag; Fig. 7 shows a reader device for employing application data in a password area; shows a system for employing memory capabilities of tags with a number of tags, reader devices and networked computers according to the invention; shows schematically a side view of a chip-bonding process; shows schematically a top view of a chip-bonding process; shows a system for manufacturing tags with application data stored in a password memory; shows a method for manufacturing tags with application data stored in a password memory; shows schematically a part of an example life cycle of a remote- access apparatus; shows schematically a method of collecting raw data and calibration data using a remote-access apparatus during its life cycle, and method of determining temperature using collected data; shows temperature measurement arrangement as an illustration of utilizing memory capabilities of a tag; shows the process of calibrating remote-access apparatuses in a single run; shows the process of incrementally calibrating remote-access apparatuses; shows the process of determining the value of an environment variable using calibration data, that is stored on at least one storage device; and Fig. 15 shows the process of measuring values of a quantity in one environment and determining the corresponding values of an environment variable in another environment. Detailed Description of the Embodiments

In the following, several embodiments of the invention will be described in the context of radio frequency identification (RFID) tags. It is to be noted, however, that the invention is not limited to RFID tags and systems only. In fact, the different embodiments have applications widely in any environment where advanced functionalities and memory capabilities of small devices with limited power supply are needed.

It has been noticed in the context of this invention that certain advanced app- lications of RFID tags would require active RFID tags (such tags that have a power supply), and that this would in turn make the tags more complicated and more expensive. Alternatively, straightforward implementtation of advanced functionality on passive RFID tags would increase the power consumption of the tags and thereby reduce the effective reading range or operational range of the tag. Various embodiments of the invention are envisioned to be used with RFID tags that are energetically essentially passive, that is, with tags that operate essentially while being in the reader field and being able to draw energy from the field. In various embodiments of the invention, some of the processing required by the advanced functionality of a passive RFI D tag may be carried out in the reader device or elsewhere in the system. This makes it possible to reduce the power consumption of the RFID tag and for the tag to have an improved operational range. The invention may help to keep the tag electronics simple and thus usable in weaker reader fields and/or longer reading ranges. On the other hand the invention may also reduce need for powerful readers to compensate for the tag power consumption. The latter benefit may be significant in some environments with many readers in the same area and/or where interfering electromagnetic fields need to be kept to a minimum. In the invention, it has been noticed that simple and passive tags and other devices may not be equipped with memory for storing data, for example for utilizing advanced functionality of a tag. In addition, it has been noticed that there may arise needs for protecting some of the data from unauthorized access, and that providing such mechanisms may be difficult to implement, energetically expensive (leading to disadvantages mentioned above), and/or such that they lead to solutions that are specific to a tag type or a tag manufacturer, thus making it more difficult to employ such tags more widely. All and any one of these problems have been identified in the context of this invention.

In various embodiments of the invention a surprising feature of some password memory fields of RFID tags and other devices is utilized. Namely, in some devices, a password field may be implemented for the sake of gaining access to some functionality, the password being a so-called shared secret, a signature, or derivable from known data by a secret algorithm. A finding in the invention is that once a password has been set in the memory, it may not be needed for anything else than comparing with an incoming password candidate. The password may therefore, surprisingly, be used to store appli- cation data, in other words, application data may be encoded into a password. Thereby the password may now serve two functions: operate as a password and carry application data for reading. This may be advantageous in devices that otherwise have little memory or have no tamper-proof memory (a password field may often be implemented in a tamper-proof manner). In addition, as a further surprising effect, some password fields may be protected by another password, and thereby such a field may serve as secure storage for application data. The above advantages may be present in any electronic device, and they may be especially advantageous in devices that are simple and energetically essentially passive.

Functionalities such as computing a measurement value and managing information security may be carried out in the reader or a network computer, and implementing such advanced functionality in a traditional manner could increase the power consumption of the tag significantly. A novel arrangement according to some embodiments therefore also makes it possible to implement advanced functionality to a passive tag. For example, a temperature measurement may be implemented using a passive RFID tag wherein some of the measurement processing is carried out at the reader or the rest of the system. The various embodiments also make it possible to implement storing advanced functionality codes and/or advanced functionality data into a pass- word field, and the password field may be protected from unauthorized access by a further password.

In certain cases it has been noticed in the invention that it may be problematic if it is not known what operations the rest of the system is required to carry out. These operations may e.g. be such that they are not governed by any standard such as the UHF Gen 2 standard. An advanced functionality code has been invented to alleviate this problem. An advanced functionality code is a piece of information associated with the tag and communicated to the reader (or the rest of the system) so that the advanced functionality pro- vided by the tag is then known. For example, an advanced functionality code may indicate that a passive tag provides an advanced functionality of a temperature measurement arranged so that part of the required processing is carried out at the reader device. The tag may send this advanced functionality code to the reader device, and the reader may then adjust its operation accordingly. As another example, the advanced functionality code may indicate an allowed condition for using or accessing the tag, for example by indicating who is allowed to used the tag, when the tag is allowed to be used, or a geographic range where the tag is allowed to be used. The advanced functionality code may be stored into a password field.

In certain other cases it has been noticed in the invention that carrying out an advanced functionality in a distributed manner between the tag and the rest of the system may require some additional data that is not easily available to the system. For example, such additional data may be advanced functionality data that can be used in carrying out the advanced functionality of the tag. The advanced functionality data may for example be information specific to the tag to enhance the advanced functionality, a mathematical formula, or an access key or access code, or any other data that are specific to the tag, specific to the advanced functionality, specific to the system or otherwise associated with the tag. The advanced functionality data may be carried on the tag in a memory, or it may be accessible to the system by means of iden- tifying the tag and using the identifier as key to accessing the advanced functionality data. The advanced functionality data therefore enables the use of the advanced functionality of the tag, or improves the use of the advanced functionality. The advanced functionality data may be wholly or partly stored into a password field. For example, if part of the advanced functionality data is stored into a password field protected by an access password, using the advanced functionality may be prevented even though some advanced functionality data resides in a normal, accessible memory. The advanced functionality code and the advanced functionality data may be stored on the chip or elsewhere on the tag either in easily accessible form or in protected form for example behind an access key or in encrypted form.

The embodiments of the invention provide advanced functionality for RFID tags and systems employing RFID tags, and a way for storing related information in an efficient and secure manner. The RFID tags and readers may operate according to a standard, and the advanced functionality code and advanced functionality data may be used to enhance the operations of passive RFID tags. For example, the RFID tag may carry in its memory the in- formation necessary to carry out a function that goes beyond the standard. As an example, the determination of temperature may be considered, and the calibration data or a part of the calibration data for the temperature measurement may be stored in the password memory of a tag. Further, temperature readings may be encoded into a password memory of a tag to store temperature history information on the tag.

For some applications it may suffice to use the advanced functionality code only, and advanced functionality data may not be required. For some other applications, the advanced functionality data may contain information that is necessary for the use of the advanced functionality, or the advanced functionality data may enhance the operation of the advanced functionality. The advanced functionality code AFC and the advanced functionality data AFD may for example be such that the AFC informs the reader that the tag is suitable for temperature measurement, and the AFD provides information to be used in the determination of the temperature. The AFC and/or the AFD may be stored wholly or partially in a password memory of the tag. Naturally, in case the tag contains memory apart from the password memory, AFD or part of AFD can be stored also in that memory.

Figs. 1 a and 1 b show block diagrams of an RFID tag and a reader device, respectively. In Fig 1 a, a passive RFID tag 100 according to an embodiment is shown. The tag comprises a chip 1 10, a protective surface 130 and an antenna 140. The antenna 140 is electrically coupled to the chip 1 10, and the chip and the antenna are formed inside the protective surface 130. The chip may comprise analog and digital (logic) circuitry to perform its operations, and/or it may comprise one, two or more processors 120, memory 122 as one, two or more memory sections and a communication module 124 such as a radio frequency modulation circuit coupled to the antenna 140. The program and/or logic may be in the form of microcode for a processor, a gate arrangement and/or programmable logic. There may be an oscillator for determining an operating frequency for the processor.

The memory 122 may comprise executable instructions for the processor, data and information related to the operation of the tag such as en electronic product code, tag identification, check sum, passwords like an access pass- word for accessing the tag, and user data. Some of the memory may be read-only memory, and some of the memory may be writable. The memory may be write-once memory, whereby it is programmed in an early phase in the life span of a tag, or it may be write-protected by an access password. The memory may contain an access password for verifying access rights to some functionality or to a memory area. For example, an access password may be residing in the memory, and by sending the access password to the device, access is granted to a memory area. The memory area may then contain a kill password, and sending the kill password makes the tag turn inactive, i.e. kills the tag. In the invention, it has been noticed that it applica- tion data may be, surprisingly, stored into the kill password area, since reading the kill password area may not kill the tag.

The memory may contain an advanced functionality code and advanced functionality data for using advanced functionality of the tag. The advanced functionality code may indicate the advanced functionality that the tag is capable of. Likewise, the advanced functionality data may be data that can be used in employing the advanced functionality of a tag. The memory may also contain application data. The protective surface 130 may be made of plastic, paper or any other suitable material, preferably material that is flexible. The material may be electrically and magnetically non-conducting in order not to obstruct the operation of the antenna 140, or the material may be weakly conducting or conducting. The tag contains no battery for powering the processor. The basic operation of the tag is to extract energy from a reader signal, and to respond to the reader signal. This responding may happen by employing back-scatter modulation of the radio frequency field (e.g. for UHF tags), or by varying the load imposed by the tag on the magnetic field (e.g. for HF tags). Typically, the tag may send an electronic product code (EPC) and/or a tag identifier (TID), or an universal identifier (UID) code, EAN code, or any serial number as a response. An RFID tag or a device may operate according to a standard. For example, the air interface may be standardized to enable interoperability of tags and reader devices. The air interface may operate according to an UHF standard wherein the tag utilizes back-scattering modulation in communication. The air interface may operate according to an HF standard wherein the tag utilizes load variation in the magnetic field. The various pieces of information stored in the tag and sent by the tag such as the EPC code may be standardized e.g. according to a Gen2 standard. The tag and/or a reader device may be standardized as a whole. The remote-access device or a tag may have various forms. For example, the tag may comprise an inlay placed inside plastic protective layers, or inside paper or cardboard. The remote-access device may also be a tag embedded in an object, e.g. a tag inside a food package. The remote-access device may also be any object capable of operating according to the various embodiments and being otherwise energetically essentially passive. For example, the remote-access device may be a food package, container, box, barrel, pallet, vehicle or a piece of furniture like a shelf. It also needs to be understood that a remote-access device can be without definite form or it may not be an end-product. For example, a chip for an RFID device, or the combination of a chip and an antenna may form a remote-access device in an embodiment of this invention. As discussed above, any device to which an RFID inlay is attached, may make up a remote-access apparatus.

Fig. 1 b shows an RFID reader device 150 according to an embodiment for reading information from tags. The reader device 150 comprises digital and analog circuitry for communicating with RFI D tags. The reader device may comprise one, two or more processors 160, memory 162 as one, two or more memory sections and a communication module 164 such as a radio frequency modulation circuit coupled to an antenna 166. The memory 162 may comprise executable program code for the processor 160, and some of the program code and other means may be for utilizing an advanced functionality of an RFID tag based on an advanced functionality code and utilizing advanced functionality data to obtain an advanced functionality result. The memory 162 may also comprise program code for any application, and pro- gram code for reading/writing application data from/to the tag. The reader device 150 may be operatively connected (e.g. by means of a computer network, a fixed data connection or a wireless connection) to a computer or server 180. The computer or server 180 may comprise one or more processors 182, memory 184 and communication means 186 for communicating with computers and reader devices. The server 180 may comprise database functionality for storing information collected from tags through reader devices, and/or it may comprise means for utilizing the advanced functionality of a tag, e.g. by processing information received by the reader device and computing or otherwise obtaining an advanced functionality result. The server 180 may be networked with other servers, and the server 180 may alone or together with other servers provide a network service for utilizing the advanced functionality of RFID tags.

To indicate its capability to perform advanced functionality, the tag may send an advanced functionality code AFC to the reader device. This sending may be in response to a request, or it may be spontaneous and in addition to standard operation. The sending of the AFC may happen anywhere during employing the advanced functionality, e.g. before the operation, during the operation or as a last step. The RFID tag sends the advanced functionality code to the reader device and/or the rest of the system so that it may be determined that the tag is capable or suitable for providing advanced functio- nality. The RFID tag may receive a request from the reader device to send information according to the advanced functionality indicated by the AFC. Alternatively or in addition, the tag may assume a mode of operation based on sending the AFC so that it will next send information needed for employ- ing the advanced functionality. The tag may send advanced functionality information according to the advanced functionality code AFC. This information may be such that the reader device may determine an advanced functionality result using the information e.g. in computations or by complementing the information with other data. For example, the tag may send information that is useful in determining the temperature of the tag, whereas the tag alone may be unable to determine its temperature (since it may not have a sensor and a power supply to enable this). The tag may also send information it receives from another device e.g. via a wired or wireless connection. This may enable the tag to operate as a relay station or as a transceiver (receiver-transmitter) and provide another device with an RFID communication channel. The sending of information may happen in a plurality of steps, for example as responses to a plurality of requests from the reader.

The advanced functionality code AFC sent by the tag may be a code stored in the user data area and accessed by the tag when it needs to be sent. Alternatively, the AFC may be part of another code, such as the electronic product code (EPC) or the tag identifier, or an access password, or any other piece of information stored on the tag. The AFC may be a number, a series of characters and numbers, or a bit sequence. The AFC may comprise multiple non-contiguous parts. The AFC enables the reader device and/or the system beyond the reader device to determine that the tag provides an advanced functionality. The tag may have specific physical or programmatic means for providing this functionality, or the tag may be a regular tag that has been determined to be suitable for use in employing the advanced functio- nality. The advanced functionality code may indicate that the tag is allowed to be used for the specific functionality, e.g. the tag may be approved or licensed by the manufacturer for use with this functionality. The presence and use of the AFC may indicate that the tag is able to perform the advanced functionality with certain accuracy. In addition, the AFC may indicate that the tag carries additional information such as advanced functionality data for using the advanced functionality. The advanced functionality code may also indicate the configuration of the tag, e.g. to indicate whether the tag is able to store advanced functionality results and/or whether some of the data on the tag is stored in a protected form. For example, an AFC for temperature measurement may indicate that the tag contains data for the temperature deter- mination, that this data is in protected form, and the tag is able to store temperature values determined by the reader. There may also be more than one advanced functionalities provided by a tag, associated with one or more advanced functionality codes. The reader device may request the RFID tag to send any advanced functionality code it has. This request may be a separate request or it may be a request according to a standard, whereby the tag interprets a standard request to mean that it should send the AFC. The reader device may then receive an advanced functionality code and determine that the tag is capable of providing the advanced functionality. Based on receiving the AFC, and/or based on other knowledge, the reader device then requests information from the tag, wherein the information is needed for using the advanced functionality. This information may be regular information provided by the tag according to a standard, or it may be additional information. The requesting may happen in a plurality of steps, or in one step. When the reader has received the information, it may then use the information to utilize the advanced functionality according to the AFC. For example, the reader may determine the temperature of a tag from timing responses of a tag by carrying out computations based on the response and/or accessing data tables. The reader may also improve the use of the information by utilizing other data indicated by the AFC. For example, the reader may use a key to access information stored on the tag for the temperature calculation.

The methods carried out by the RFID tag and the reader device may be interlinked so that some the method steps of the RFID tag happen in response to the method steps of the RFID reader device and vice versa.

As described earlier, the tag may send information for utilizing an advanced capability according to an advanced capability code AFC. The sending of the information may also happen without any advanced capability code. The tag sends information related to an advanced capability, possibly as a response to a request from a reader. Related to the use of advanced functionality, the tag may carry additional data for using the advanced functionality. For example, the tag may comprise data for a temperature measurement or another type of measurement, or the tag may contain a section of data that can be utilized in using the advanced capability. The tag may fetch the AFD from a memory either internal to the chip or in some other manner operatively connected to the tag. The tag then sends this advanced functionality data AFD to the reader device so that the AFD can be used or stored at the reader device and/or one or more other devices in the system for utilizing the advanced functionality.

The advanced functionality data AFD may be a data table or a data structure, functionality parameters, a definition of a mathematical function or any other data structure or object that may be used in utilizing the advanced functional- ity. For example, the AFD may comprise a single number, a series of numbers, a data table, a plurality of data tables, a data structure, an object definition and data, a database, and/or any combination of these alone or together with other information. The AFD may comprise a single packet of data, or the AFD may be distributed across a plurality of packets. The AFD may be com- plete and usable as such, or it may be such that it is augmented by other data and/or code that resides elsewhere in the system to save memory on the tag. The AFD may be intended to be used in the advanced functionality, or it may be intended for presenting the result of an advanced functionality (such as HTML code or XML representation, or a Adobe PDF file, Word doc- ument or Excel worksheet).

As described earlier, the reader device may request information relating to the advanced functionality, and receive the information. This information may be received at any time during the employing of the advanced functionality, e.g. before, during or after any receiving of advanced functionality data. The reader may then, with respect to an AFC and/or based on other knowledge, request advanced functionality data from the RFID tag. The tag may also send the data on its own so that a request is not needed. The reader device then receives the AFD and utilizes the AFD with the received information to e.g. obtain an advanced functionality result. The use of the AFD may happen at the reader device and/or elsewhere in the system. The AFD may be in protected form, whereby the reader device may form and/or use a key to access or decrypt the AFD before using it.

The tag may send information relating to an advanced functionality so that a reader device can use this information to utilize the advanced functionality of the tag. An advanced functionality result may be derived by the reader and/or the rest of the system. The tag may then receive the advanced functionality result alone or together with other data from the reader or from another device. The tag may store this advanced functionality result into a memory together with earlier received advanced functionality results, with other data and/or alone. The tag may store the result as such or the tag may process the result or combine it with other data before storing the result. The tag may even form advanced functionality data AFD by using the received result. The tag may store the received data and/or result in a protected or unprotected form, e.g. by using an access password and/or encryption methods. There may be other information received and stored by the tag, too, such as time and location information. The tag may also send advanced functionality data to the reader. For example, the tag may receive the temperature determination result from the reader and store it onto its memory in protected form behind a password or in encrypted form.

The reader may receive information from the tag related to advanced functionality, as explained above, possibly with advanced functionality data AFD. The reader device and/or the rest of the system may then determine an advanced functionality result, as explained earlier. The reader device and/or another device in the system may then choose to send the result back to the tag so that it can be stored on the tag in addition to or instead of storing it in the reader or in a database in the rest of the system. For example, the reader may send the result of a temperature computation to the tag so that the tag can store the temperature information at the tag. The reader may send other information than the result to the tag, too, for example location information and/or time information. This may allow the tag to e.g. store a temperature history with time and place of the item whose temperature is being monitored. This may be especially useful e.g. in cold chain management of perishable items or other temperature managed chains, where knowledge and control of the temperature history of an item is of importance. The advanced functionality data may be in a protected form in either the tag memory, in the reader memory or in an external database. The protection may have been carried out so that the AFD resides in a memory area pro- tected with an access key, or so that the AFD has been encrypted or scrambled using an algorithm dependent on an access key. The AFD may be wholly or partly stored in a password field of the tag, and the rest of the AFD may reside in normal memory on the tag, or in the reader, or in an external database.

The access key may be stored on the tag memory or a seed for generating the access key may be stored on the tag memory. An algorithm may be used to generate the access key from the access key seed, wherein the algorithm is such that it is unlikely that two different algorithms would produce the same exact access key. Moreover, it may be desirable that the algorithm is such that two different seeds are unlikely to produce the same access key.

The seed or the access key may be a value stored on the tag, for example the electronic product code or part of it, the tag identification or part of it, or another unique identifier or a combination of these or any parts of these. As an example, the access key may be an EPC (electronic product code) Class I Gen2 compliant access key for accessing locked memory areas of the tag. The EPC access key may be calculated from the EPC on the tag e.g. with a hash function, an XOR function with a mask, as a digital digest or another cryptographic key. The EPC may also be used as an index to a table of access keys e.g. cryptographic keys. The length of the key may be less than the length of the seed, it may be the same length or it may be longer. For example, the EPC may be 96 to 240 bits long, and the access key may be 32 bits long. Bit puncturing may be used in shortening the key and bit padding may be used to lengthen the key. A memory area containing data for the advanced functionality, e.g. the AFD, may be locked using the access key and can only be opened using the access key formed from the EPC or another seed. For example, the AFD may be stored in a kill password of a tag, protected by an access password. The locking and opening or encryp- tion and decryption may be done in a symmetric manner wherein the encryption and decryption keys are the same, or it may be done in asymmetric manner, where the keys are different. A public key infrastructure (PKI) may be used for the latter. Every tag in the system may have a different access key (if the EPC or other seed on the tag is different), and the reader or the system can calculate the access key using the seed from the tag. Using this access key, the reader or the system can access or decrypt the AFD located on the tag or in an external database.

As an example, temperature calculation may happen so that the reader requests information from the tag that it can use for temperature measurement, and in order to achieve a result, it uses data stored on the tag in the measurement. The reader may have determined by using an AFC that the tag is suitable for temperature measurement. The advanced functionality code AFC may be part of the electronic product code indicating, for example, that the item is a perishable product and therefore its temperature needs to be monitored. The AFD may be data for calculating or determining the temperature of the tag from local oscillator frequency shift polled from the tag. The reader may request the data from the tag, and the data may reside on the tag in protected form, e.g. on a protected memory area or in encrypted form. The reader therefore uses an algorithm to obtain an access key based on the EPC or tag identification, and then unprotects the data using this access key. The unprotecting may happen e.g. by opening a protected memory area on the tag or by decrypting the data. The unprotected data, for example calibration information, may then be used for calculating the tag temperature. The access key may also be used to write data onto the tag in protected form, e.g. in a protected memory area or in encrypted form.

The protection algorithm may be a secret algorithm known only to the reader device or the system, or it may be a widely public algorithm. The algorithm may depend on the advanced functionality code. The data protected on the tag may be advanced functionality data or it may be any other data.

Figs. 2a and 2b show methods for reading data from a remote-access device (such as an RFID tag, or another electronic device, or a device where RFID functionality exists) according to an example embodiment. In Fig. 2a, access to read a password may first be granted in phase 220. This access may be granted on the basis of the device receiving an access password or an appropriate message to grant access to a password field. Alternatively, the access may be granted by default, e.g. so that the password field is readable to anyone attempting to read it with the correct command. Therefore, there may not be an access grant step at all. In phase 220, the password is read from the password memory. There may be a specific command for the reading received by the tag. For example, the remote-access device such as an RFID tag may receive an access request together with an access password. The RFID tag may then grant access to read a kill password (a password that can be used to inactivate the tag). The kill password may then be read and transmitted back to the reading device. The operation described above may happen according to a standard, such as the UHF Gen2 standard for RFID tags.

In step 240, a bit string of the password (whole or part of the password) read in phase 220 may be converted to a number or to a text, i.e. data suitable for use in an application. For example, the data may undergo type conversion, whereby a bit string is converted or interpreted as a certain data type, such as a floating point number (e.g. 16, 32 or 64 bits), an integer (e.g. 8, 16 or 32 bits), a character (e.g. 8 or 16 bits), or a logical TRUE/FALSE flag (e.g. 1 bit). Alternatively or in addition, a password bit string (whole or part of the password) may be mapped to a value using a data table or a function. Alternatively or in addition, the data in the bit string may be decoded or decrypted in another manner, e.g. by applying an XOR operation with another string before or after conversion, or by decrypting the string with a decryption key. The data may be converted to a data structure or an object, or used in a program. For example, the data may be converted to calibration coefficients for calibrating a temperature measurement carried out with the help of the remote-access device. In phase 260, the data formed in step 240, or the whole or part of the password read in phase 220 may be provided to be accessible to an application e.g. by storing it in a freely accessible memory or by transmitting it to another device such as a reader device for reading RFID tags. The above phases may be carried out in another manner than described, for example, a password field may be read with a single command.

Fig. 2b shows a method for reading data from a remote-access device such as a tag by using a reading device. In phase 210, the reading device may send a request to access a password area, e.g. by sending an access password and/or an appropriate message to the remote-access device. The reading device may also send a message to request the data in the password area, or the request may be in the same message as the access request, or an access request may at the same time be a request to read the data in the password area. The remote-access device may then perform actions, e.g. those described in the context of Fig. 2a, to provide the password data. The password data or data derived from the password data may be received at phase 270.

At phase 270, a bit string of the received password data (whole or part of the password) may be converted to a number or to a text, i.e. data suitable for use in an application. For example, the data may undergo type conversion, whereby a bit string is converted or interpreted as a certain data type, such as a floating point number (e.g. 16, 32 or 64 bits), an integer (e.g. 8, 16 or 32 bits), a character (e.g. 8 or 16 bits), or a logical TRUE/FALSE flag (e.g. 1 bit). Alternatively or in addition, a password bit string (whole or part of the password) may be mapped to a value using a data table or a function. Alternatively or in addition, the data in the bit string may be decoded or decrypted in another manner, e.g. by applying an XOR operation with another string before or after conversion, or by decrypting the string with a decryption key. The data may be converted to a data structure or an object, or used in a program. For example, the data may be converted to calibration coefficients for calibrating a temperature measurement carried out with the help of the remote-access device.

At phase 280, the data may be provided to an application or used in the operation of an application. For example, as described elsewhere in this application, the reading device may utilize advanced functionality of a remote-access device (such as a passive RFID tag), and may e.g. determine local oscillator information from the tag for calculating a temperature of the tag. The reading device may use data received from a password field such as the kill password of a tag to improve the advanced functionality, e.g. calibrate the temperature measurement. For example, the received data may be used as coefficients in a conversion function from local oscillator information to a temperature. The data may be utilized in the reading device, and may be supplemented by data from elsewhere than the remote-access tag, or the data may be utilized in another device, e.g. a network server.

Figs. 3a and 3b show methods for writing data to a remote-access device according to an example embodiment. In Fig. 3a, the remote-access device receives application data in phase 340 to be written to a password area. The received application data may be numbers, text, logical data, structured data or other, or the application data may be already formed into a format suitable for storing into a password field. The data may be converted to be suitable for storing into a password field in phase 350, e.g. by packing, type conversion, mapping into discrete elements in a data table, or by another encoding, and possibly encrypted. For example, two 16-bit floating-point numbers may be received and their bit strings may be concatenated for storing into a 32-bit password field like the kill password.

The storing of the application data in password format into a password field may require an access to be granted for the operation. For example, an access password may be received, and used for granting access to write into a password field such as the kill password field. Granting access for writing into a password area may happen in phase 360. In phase 370, the received and/or converted application data is written into a password field. For example, calibration coefficients for temperature measurement may be stored into a kill password of a tag that is capable of being used for temperature measurement. The password functionality of the application data may still be in operation although the stored data in the password field is now application data. For example, a tag may still be deactivated by sending the kill password (containing application data) to the RFID tag.

In Fig. 3b, the storing of application data by a reading device into a remote- access device password field is shown. In phase 310, the application data to be stored is determined. For example, the application data may be data specific to the remote-access device such that it is advantageous to carry it on the remote-access device. The application data may be an advanced functionality code or advanced functionality data, or part of the same, such as temperature capability code and/or calibration data for the temperature measurement, and/or temperature history of the tag. In addition, any other data such as location data, reading device identification, or data to be used in any application may be used here.

In phase 320, the application data may be formed into a password format for writing into a password field. The data may be concatenated and thereby formed into a bit string. The data may also be converted to be suitable for storing into a password field in phase 350, e.g. by packing, type conversion, mapping into discrete elements in a data table, or by another encoding, and possibly encrypted. For example, two 16-bit floating-point numbers may be received and their bit strings may be concatenated for storing into a 32-bit password field like the kill password. In phase 330, the formed password may then be sent to be written to the remote-access device, accompanied by appropriate protocol commands. In addition, an access request and/or an access password may be sent to gain access to writing into a password field. For example, an access password may be sent to gain access to writing into a kill password field on an RFID tag.

In Figs. 2 and 3, the advanced capabilities of a tag with advanced capability code and advanced capability information may be carried on the tag in a protected form. The tag may send advanced functionality data AFD to the reader in protected form. The AFD may, in other words, be in encrypted or in scrambled form. The reader may then receive and store the AFD. The tag may send key information to the reader device and/or the rest of the system. It is possible that this tag key information is the EPC or the tag identifier and the seed or actual key information resides in a database in the system. The reader and/or another element in the system may received this key information. Using this key information, the reader or another element in the system may form an access key. This access key may then be used to unprotect or decrypt the received data, or to unprotect or decrypt other data related to the tag. The above phases may happen in the tag and at the reader or rest of the system in an independent manner or dependent from each other. The different phases may happen in another order than described here.

Alternatively, the tag may send key information to the reader device and/or the rest of the system. It is possible that this tag key information is the EPC or the tag identifier and the seed or actual key information resides in a data- base in the system. The reader and/or another element in the system may receive this key information. Using this key information, the reader or another element in the system may form an access key and send it to the tag. The tag may receive the access key and use it to unprotect or decrypt advanced functionality data AFD residing on the tag. The tag may then send the unprotected AFD to the reader. The reader may then receive the AFD and use it to utilize the advanced functionality. The tag may unprotect and send other data than AFD using the access key. The above phases may happen in the tag and at the reader or rest of the system in an independent manner or dependent from each other. The different phases may happen in another order than described here.

Alternatively, the reader may request advanced functionality data AFD or other data from the tag. The tag may fetch key information (e.g. EPC) from memory, and form an access key using the key information. The tag may then unprotect advanced functionality data AFD residing in the tag memory by accessing a password-protected memory area or by decrypting the AFD. The tag may then send the unprotected AFD to the reader device. The reader may receive the AFD and use it to utilize the advanced functionality provided by the tag. The above phases may happen in the tag and at the reader or rest of the system in an independent manner or dependent from each other. The different phases may happen in another order than described here. In the methods according to Figs. 2 and 3, there may be other steps than the ones shown in the figures and described above. For example, the advanced functionality code and its use and the storing of the advanced functionality result have been omitted. Figs. 4a and 4b show tags with application data stored in a password area, and with application data stored in a password area and protected by an access key. In Fig. 4a, a tag 400 or any other electronic device with application data stored in a password area is shown. The tag may comprise elements as described in the context of Fig. 1 a, and has a memory for holding various pieces of information. There may be a password area 412 for storing a password, and for storing application data converted into a suitable form and for storing as a password, a memory 414 for the electronic product code and a memory 416 for the advanced functionality code AFC and a memory 418 for advanced functionality data AFD. The various memory areas may be implemented in the same memory, or they may be implemented in different memories. Some of the memory may be read-only memory, or write-once memory, or protected from unauthorized access in some way. In other words, the device (or tag) 400 is such that it contains application data in a password memory area (an area reserved for storing a password). In Fig. 4b, a tag 470 with application data in a password area is shown. The tag comprises elements as described in the context of Fig. 1 a, and has a memory for holding various pieces of information. There may be a password area 412 for storing a password and application data in/as the password, a memory 414 for the electronic product code and a memory 618 for advanced capability data AFD. The password area 412 PASSWORD 1 may be protected from read and/or write access by another password PASSWORD 2, e.g. an access password. One or both of the PASSWORD 1 and PASSWORD 2 may contain data indicative of application data, or application data as such. The application data may be extracted/decoded from the PASSWORD 1 and/or PASSWORD 2 fields by a separate operation, or by a simple type conversion. The various memory areas may be implemented in the same memory, or they may be implemented in different memories. Some of the memory may be read-only memory, or write-once memory, or protected from unauthorized access in some way. The tag may also comprise a tag ID or other identification information. The data area 418 has been arranged to be such that the AFD is stored in protected form, for example in a password-protected or encrypted memory 430. The memory 430 may be protected e.g. by encryption using as a password or encryption key or a seed for a password or encryption key at least part of one or more of the data in the ID field 420, the EPC field 418, the PASSWORD 1 area 412 (e.g. KILL password) or the PASSWORD 2 area. A tag may combine any or all functionalities as explained in the context of Figs. 4a and 4b.

Fig. 5 shows a memory configuration of a tag according to an example embodiment. The tag may contain a contiguous memory space, or the memory space may be split into a plurality of contiguous memory spaces, or the memory may comprise permanent registers for storing individual data items. For example, the memory may comprise sections for user data USER 510, for tag identification data TID 530, for electronic product code data and related data EPC 550, and for other data such as passwords RESERVED 570. The various sections may comprise data items e.g. as follows. The user data area 510 may comprise a number of data words. The data words may be e.g. 8 bits, 16 bits, 32 bits or 64 bits long, or even 12 bits, 30 bits or another irregular length. The tag identification may comprise one or more tag identifiers. The tag identifier TID may be stored e.g. in one 16-bit data word, or in two 16-bit data words (being 32 bits in length). The electronic product code EPC may comprise a number of parts EPC(1 )-EPC(N), and/or there may be a number of EPC codes stored on a tag. In addition, there may be a STORED PC value and a STORED CRC value in the memory for verifying the contents of the EPC memory area. In the RESERVED memory area 570 there may be various passwords stored such as an access password for accessing some memory areas like the kill password, and the kill password for inactivating a tag.

Fig. 6 shows a method for deriving application data from a password memory of a tag. In phase 610, a password area may be accessed e.g. by providing an access password (the access password being different from the password being accessed), as described earlier. In phase 620, password data may be read from the accessed password area. In case the password bit string is in encrypted form, the password bit string may be decrypted in phase 630 before decoding. The decryption may happen using data on the remote- access device or on the reading device or data from a server, e.g. by applying an XOR operation with another string before or after decoding, or by decrypting the string with a decryption key. In phase 640, the decision of employing zero, one or more decoding methods to the password bit string or a part of the password bit string is made.

In phase 650, in case the bit string or part of it is in an appropriate format, it may be converted to application data by simple interpretation or type conversion. For example, if there are 16 bits in the password bit string that represent a 16-bit floating point number, the 16 bits of the bit string may be converted to or interpreted as a floating point number, such as "+1 .27°C" indicating a temperature or a calibration coefficient for calculating a temperature. The 16-bit floating point number may also contain information indicative of one or many correction terms of calibration data. As another example, an string of 7 or 8 bits may be interpreted as a character such as a "T", serving as an advanced functionality code for temperature measurements. In phase 660, a bit string may be mapped to a value using a table. For example, two bits of the bit string may form bit patterns "00", "01 ", "10" and "1 1 ", and these can be mapped to values like "-5°C", "-2°C", "+1 °C" and "+3°C", for example indicating a past temperature reading of a tag, or a calibration coefficient for calculating a temperature. The decoding methods may be combined, e.g. type conversion and mapping may be applied in sequence. In phase 670, the data may be provided to an application by storing them in a memory, by providing them to be accessible over an interface, or by sending them to another device.

Fig. 7 shows a reader device 700 for employing application data in a password area. The reader may comprise elements as described in the context of Fig. 1 b, and has a memory for holding various pieces of information. The reader device may contain a block 710 for determining through the use of an advanced functionality code whether a tag is capable of an advanced functionality. The reader device may also contain a program 720 for utilizing advanced functionality. The reader device may implement all or some of the advanced functionality operations as circuitry 730, e.g. to increase speed. The reader device may also contain memory 740 for holding advanced func- tionality data AFD received from an RFID tag. The memory 740 may also contain password information for accessing functionality and/or memory of a tag. For example, the memory 740 may contain an access password for accessing the kill password area of a tag. The memory 740 may also contain some or all of advanced functionality data AFD for using advanced functio- nality of a tag. For example, the memory may comprise temperature calibration information of a tag, whereby the tag contains a part of the temperature calibration information in a protected memory, e.g. the kill password memory area. The AFD, e.g. the calibration information, on the tag and on the reader may then be combined to use the advanced functionality of the tag, e.g. to determine temperature of the tag. Furthermore, the reader device may com- prise functionality for determining time and location information so that it can be associated with the advanced functionality results.

Fig. 8a shows a system for employing memory capabilities of tags with a number of tags, reader devices and networked computers according to the invention. The system may comprise a number of reader devices 800, 801 and 802. The reader devices may be geographically at the same location or at different locations. As explained in the context of Fig. 7, the reader devices may comprise blocks for determining the advanced functionality 803, advanced functionality program 804, circuitry for advanced functionality 806 and memory 808 for advanced functionality data and passwords. The system may comprise a number of tags 810, 812 and 814. The tags may be capable of similar or different advanced functionality, and may contain similar or different advanced functionality codes AFC and advanced functionality data AFD. The tags may comprise various passwords PW1 and PW2 in addition to or instead of AFC and/or AFD. For example, the tags may contain an access password for preventing unauthorized access to some tag areas, and/or a kill password for turning the tag inactive. Especially the advanced functionality data may be tag dependent, e.g. tag specific information. The system may also comprise a number of computers and/or servers 820 and 822 for providing a service related to the advanced functionality. The system may also comprise one or more databases for holding data and results related to the advanced functionality. The various elements of the system may be in a communication connection with each other, e.g. through a data network, or peer-to-peer connections from one element to another. The communication connections may be wired or wireless, e.g. an IP-based connection over a fixed network, a wireless local area network or a mobile communication network. A remote-access apparatus may comprise one, two or more processors 120, memory 122 as one, two or more memory sections and a communication module 124 such as a radio frequency modulation circuit coupled to the antenna 140. The remote-access apparatus may also contain a local oscillator. The remote-access apparatus may be substantially passive, i.e. energy for operating these units may be extracted from a radio frequency field. Energy for operating the units may be extracted from interrogation signals sent from a reader. In addition, the reader device may provide the remote- access apparatus with the operating energy.

An energetically essentially passive remote-access apparatus may comprise a capacitor or a rechargeable battery for storing operating energy extracted from an interrogation signal. Operating energy for operating the apparatus may be extracted from one or more interrogation signals sent from one or more readers. The local oscillator may be used to measure a value of an environment variable, such as temperature, when the frequency of the local oscillator depends on this environment variable. In other embodiments, the RFID transponder may comprise another oscillator or a temperature sensing unit for this purpose.

The remote-access apparatus may respond to a reader signal. A carrier frequency of the response may be modulated at a modulation frequency †LF- The modulation frequency LF may also be called as a "link frequency". The modulation frequency †LF of the response may, in turn, depend on the clock frequency fcLK Of a local oscillator. Thus, also the modulation frequency †LF may depend on the temperature of the chip. A change of the modulation frequency †LF may indicate a change in the temperature. Consequently, the modulation frequency †LF may be interpreted to be temperature data.

The local oscillator may be e.g. a ring oscillator. A ring oscillator may comprise e.g. a plurality of cascaded logical gates whose operating speed depends on the temperature. The local oscillator may be e.g. a relaxation oscillator.

The transponder may be arranged to determine a frequency parameter NC, which depends on the frequency of the local oscillator. In particular, the frequency parameter NC may indicate the number of pulses of the local oscillator corresponding to the duration of a frequency-setting parameter. In parti- cular, the frequency parameter NC may be substantially equal to the parameter BLF (backscatter link frequency), as defined in the EPC Gen2 protocol. The frequency-setting parameter may refer to the parameter TRCal, as defined in the EPC Gen2 protocol.

The frequency parameter NC comprises information about the temperature when the frequency of the local oscillator depends on the temperature.

The remote-access apparatus may be arranged to operate such that a response sent by the apparatus comprises a binary number corresponding to the value of the frequency parameter NC.

The frequency parameter NC may be stored in a memory. The apparatus may be arranged to operate such that a response sent by the apparatus comprises a binary number corresponding to the value of the frequency parameter NC.

The apparatus may be arranged to operate such that the value of the frequency parameter NC is sent as a binary number only when the interrogation signal contains a request for said value. The apparatus may comprise a temperature sensor, which is different from the local oscillator. The temperature sensor may comprise e.g. a P-N junction, a resistive element, whose resistance depends on the temperature, or a thermocouple. The resistive element may be e.g. a NTC or PTC resistor (NTC refers to negative temperature coefficient, and PTC refers to positive temperature coefficient. The resistive element may be a Pt100 sensor.

The temperature sensor may be located in a sensor module. Furthermore, the RFID chip may comprise the temperature sensor or sensor module, or the sensor or the sensor module may be external sensor to the chip. The RFID transponder may comprise the sensor or the sensor module.

The temperature sensor may be powered by energy extracted from a radio frequency field. The temperature sensor may be powered by energy extracted from a radio frequency field of one or more interrogation signals. The apparatus may be arranged to convert an analog signal provided by the sensor into temperature data. The temperature data may be stored in a memory e.g. as binary data. The apparatus may be arranged to transmit the temperature data to a reader e.g. when requested by an interrogation signal.

An interrogation signal sent from a reader to an apparatus may comprise a frequency-setting parameter TRcal (reference is made to the EPC Gen2 protocol). The apparatus may be arranged to set a modulation frequency ("link frequency") †LF based on the value of the parameter TRcal. The value of the TRcal may be directly proportional to the temporal duration of the data sequence TRcal. The value of the parameter TRcal may be e.g. 50 με.

The apparatus may be arranged to set the modulation frequency †LF accord- ing to the following equation:

PR L ^{F ~} TRcal

The modulation frequency †LF may also be called as a "backscatter link fre- quency".

In practice, the transponder may be arranged to calculate the modulation frequency †LF by using integer numbers as follows: where DR denotes a division ratio parameter. The value of the division ratio parameter DR may be e.g. 8 or 64/3. † _C LK denotes the frequency of the local oscillator. ROUND denotes a rounding or truncating function, i.e. it rounds or truncates an arbitrary number format to an integer number.

When the value of the frequency-setting parameter TRcal is increased, the modulation frequency † _L F may decrease in several (abrupt) jumps J1 , J2, .., as can be derived from the equation. The modulation frequency † _L F may be substantially constant between TRcal values corresponding to two adjacent jumps J1 , J2, provided that the clock frequency†CLK is constant.

When the value of the frequency-setting parameter TRcal is varied by a small amount in the vicinity of a jump, the clock frequency †CLK being substantially constant, the modulation frequency †LF may be abruptly change from the value †LFI to the value †LF2-

It may be derived from the above equation that

In other words, the clock frequency † _C LK may be calculated from the upper modulation frequency † _L FI and lower modulation frequency † _L FI associated with a single jump.

A first response modulated at the first frequency † _L FI may be provided by sending a first interrogation signal from a reader to the apparatus such that the first interrogation signal comprises a first frequency-setting parameter TRcaM . A second response from the same apparatus modulated at the second frequency f _L F2 may be provided by sending a second interrogation signal from a reader to the apparatus such that the second interrogation signal comprises a second frequency-setting parameter TRcal2.

The time period between sending the first and second interrogation signals may be selected to be so short that the temperature of the local oscillator is not significantly changed during said time period.

Thus, the method for monitoring the temperature may comprise:

- sending a first interrogation signal and a second interrogation signal to the remote-access apparatus,

- receiving a first response signal from the remote-access apparatus at a first modulation frequency {† _L FI) and a second response signal from the remote- access apparatus at a second modulation frequency( f _LF 2), wherein the first response signal is a response to the first interrogation signal and the second response signal is a response to the second interrogation signal,

- determining a clock frequency / i/ from the first modulation frequency( z.Fi) and the second modulation frequency( †LF2}-

The determined clock frequency †CLK comprises temperature-dependent information. For example, a change in the clock frequency / i _/ may indicate a change in the temperature.

The relationship between clock frequency †CLK and absolute temperature values may be established e.g. by calibration measurements.

In addition to height of the frequency jump, a frequency-setting parameter that matches with a jump, may also depend on the temperature or another environment variable. For example, denoting the frequency-setting parameter that matches with the jump number 1 by TRcaM , TRcaM may depend on the frequency of an oscillator, and thereby also on the value of the environment variable.

As discussed, both the clock frequency and the a frequency-setting parameter that matches with a jump may be measured using a remote-access apparatus. These quantities will thus be called measurable quantities. As discussed above, a remote-access apparatus may be used for measurements. In a typical configuration, a reader device is used in the measurements. With the reader device, some property of the remote-access apparatus may be directly measured. A quantity may be determined from at least one value of the directly measured property such that this relation does not depend on the measurement environment or the individual properties of the remote-access apparatus. Such quantities are called measurable, since they can be measured, i.e. determined from results of direct measurements without calibration. As an example, a directly measured property may be the backscattering frequency of a remote-access apparatus. From at least two such values, one may determine a measureable quantity, such as the frequency of the local oscillator of the remote-access apparatus. In addition, the backscattering frequency of the remote-access apparatus may change abruptly in response to changing the TRcal value used in the communication between the remote-access apparatus and the reader device. The back- scattering frequency is directly measurable, and TRcal value, at which this change occurs may be determined without calibration parameters, i.e. is measurable.

In an embodiment, the frequency parameter may be directly read from a remote-access apparatus using a reader device.

Furthermore, the measurable quantity may depend on an environment variable. Therefore, in some cases the value of the environment variable may be determined, once the relation between the measurable quantity and the environment variable is known. This relation can be made known by cali- brating the remote-access apparatus or a number of remote-access apparatuses. After calibration, this measurable quantity may be used to determine the temperature. In addition, some other variables, such as time or location may be measured in the calibration process, and they are called variables. Moreover, a combination of quantities may serve as the measurable quantity. E.g. a combination of the local frequency and the TRcal value of a reader device, at which the backscattering frequency of a remote-access apparatus changes, may serve as the measurable quantity. Still further, several measurable quantities may be used to determine the value of an environment variable. For example, the local frequency may be used to determine a first temperature, and the TRcal value of a reader device, at which the backscattering frequency of a remote-access apparatus changes, may be used to determine a second temperature. Then the value of temperature may be obtained as a combination of said first and said second temperatures.

The value of an environment variable may change the value of the measurable quantity. For example, temperature may change the frequency of a ring oscillator, and therefore the oscillation frequency (or oscillation period) of the oscillator may be used to determine the temperature. It is also possible, that the frequency may depend on the strain. Alternatively, if the chip is in a strained state, internal stress is induced in the chip. Moreover, external pressure may induce these internal stress and strain. Therefore, such environment variables may include temperature, pressure, stress and strain. Furthermore, if the remote-access apparatus comprises a sensing unit, an environment variable may change a measurable quantity of this sensing unit. Examples include humidity and acidity. However, the dependence between the measurable quantity and the environment variable is not generally known a priori, but needs to be found out by calibration. After calibration, the value of the environment variable may be determined based on the measured quantity. Without loss of generality, the measured quantity will be denoted by f _osc and the environment variable by T. Calibration of the remote-access apparatus means that a relation between f _osc and T should be known with reasonable accuracy. Also quite generally, some function may be used to describe this relation. It is also noted that the value of the measurable quantity may depend on some other parameters such as the RF power the remote-access apparatus derives from the RF-field generated by the reader device. The power of the backscattered signal and the power sent to the remote-access apparatus may be used to indicate the power derived by the device. In calibration, the remote-access device may be calibrated for some power levels separately such that for a given power level, a given relation between f _∞c and 7 ^~ is used. This relation may thus depend of the power.

Calibration may be done with well known curve fitting algorithms. Typically calibration measurements are performed, and some curve, i.e. function, fitted to the calibration measurement data. For example, a number of pairs {f'oscb T'i) may be measured in the calibration measurements, where f' _osc is the value of the value of the measured quantity in Ah measurement, and T is the reference value of the environment variable in Ah measurement. It should be emphasized, that T is the value of the environment variable in the remote-access device, where the measured quantity is measured. For example, 7 ^~ may be the temperature of the remote-access device, which in a stationary state equals the ambient temperature. For calibration, a function g may be used to interpolate or extrapolate the relation between these values as fosc(T)=g(T) and, since one generally wants this function to represent the calibration measurements, it is required that g(T'i)~f' _0SC for all / ^' . The function g(T) may be a polynomial, or some other suitable function. Typically, a function with only a few parameters is used, such a first degree polynomial, and the parameters are estimated with well known curve fitting techniques. Explicit examples are the first and second degree polynomials: g(T)=aiT+a ₀ or g(T)=a ₂ T ² +aiT+a ₀ , where the parameters a are estimated by curve fitting techniques and using the calibration measurement results. In some cases it may be feasible to use the inverse, i.e. use a function h such that T(f ₀ sc)= (fosc) and T'i~h(f' _osc ) for all / ^' . The functional form of h can also be a low degree polynomial, e.g. h(f _OS c)=bifosc+bo or It is also possible, that all the measured values { f' _osc ;T ), possibly arranged according to increasing f' _osc , form a lookup table that is used as h. Furthermore, it is possible, that both the quantities and the environment variables are measured as function of another variable, such as time, i.e. both the pairs {f'oscj ;t'i) and ( ;T'i) are measured, and they are combined to form calibration information only when needed. It is also possible that the pairs { f' _osc ;t'i) and (ί', ;T ) are measured with different devices and stored on different storage devices. It is also possible that all the data triplets { f _osc ;t'i ;ΤΊ) are used for calibration such that only a sufficient amount of most recent measurement values are used for calibration. This might be useful, if the dependence of the quantity on the environment value drifts in time. By these calibration mea- surements, and possibly using known curve-fitting algorithms, calibration data can be obtained. Calibration data means data that can be used to determine the value of the environmental variable T based on the measurement of a quantity f _osc . It is also noted, that by using higher than 1 ^st degree polynomials g or h , the value of the environment variable can be more accu- rately determined than with a 1 ^st degree polynomial. Moreover, it is noted, that in case higher degree polynomials are used, it is feasible to used the function h rather than g, since this allows for direct solution of the value of the environment variable. In case a higher degree g was used, one would have to solve the roots of the polynomial, and choose the correct one to determine the value.

Generally the calibration data may comprise the a parameters of the function g, the b parameters of the function h, the measured data points { f' _osc ;T'i), a set of measured data points { f' _osc ;T ) or a set of representative data points {f"osc ;T"i). A representative data point { f'Osc ;T") may be for example a aver- age value of several measured data points, i.e. the representative value denoted by two superscripts " may be the average of several measured values, denoted by one superscript '. Specifically, if many similar remote- access apparatuses are calibrated at the same time, it may be feasible to use the average value of the quantity in a specified temperature for forming calibration data. Other possibilities are to generate several representative data points from a single data point. In this way some data point may be weighed when forming calibration data. For example, data point close the expected use environment may be give more weight in the calibration than data point far away from expected environment. Furthermore, the calibration data may comprise the identity of the remote-access apparatus to which the calibration data is applicable. Still further, the calibration data may comprise the triplets {f'osc/ 'r -t ) or ( f"osc ;T" _; ;t''i).

In some embodiments also partial calibration data is measured and stored in the remote-access device, in another remote-access device, in the reader device or in an external memory. Partial calibration data is here defined as data comprising the values of the f' _osc at some instances of time or in some locations, or data comprising the values of the environment variable ΤΊ at some instances of time or in some locations. In order to form calibration data, partial calibration data needs to be combined with other partial calibration data. More specifically, a value of the environment variable needs to be associated with the corresponding value of the measured quantity, e.g. by using the measuring times. Partial calibration data comprising values of the f'oscj at some instances of time or in some locations may be measured e.g. in a first device such as an RFID reader device. The partial calibration data comprising the values of the environment variable T at some instances of time or in some locations may be measured in a second device, such as a data logger. Moreover, the combination of these partial data may be done in either of these devices, or in a third device, such as a computer. After the values f' _osc are associated with corresponding values Γ,, also other calibra- tion data, such as parameters of a function, may be formed.

The calibration data can be used to determine the value of the environment variable T based on the measurement of a quantity f _osc , the measurement result being denoted by f' _osc . For example, if the parameters of the function h are known, T'(f' _0S c)=h(f' _0SC ) and in case h is a first degree polynomial, Here f' _osc denotes the measured quantity and T is the determined value of the environment variable. In might also be possible to use a first degree polynomial g: T'+ao , and calculate F from this equation. Naturally also polynomials of higher degree may be used. Furthermore, It is possible, that all or some of the values or representative values of calibration measurements {f' _osc ;T ) or {f" _osc ;Τ") form a lookup table that is used as h. Thus, the temperature could be looked up from that table and in case an exact match is not found, the temperature can be interpolated or extrapolated using e.g. two data points that are closest to the measured f'osc, with respect to the f' _osc or f" _osc values present in the calibration data.

Calibration can be done for each remote-access apparatus individually, or calibration can be made for a set of similar remote-access apparatuses. In the former case, calibration measurements are performed for one remote- access apparatus, and the calibration data concerns only that apparatus. In the latter case, the same calibration data, e.g. coefficients a or b, may be used for a number of remote-access apparatuses. The calibration data may be obtained by measuring many remote-access apparatuses in the calibration measurements, and forming calibration data based on all the measured data. It is also possible, that the calibration data is used for a remote-access apparatus that has not actually taken part in calibration measurements. E.g. in case the RFI D chip is from the same family, it may be possible to rely on calibration measurements on similar apparatuses.

Moreover, some indications of the value of the environment variable may be obtained even without calibration, e.g. from the general knowledge of the frequency of an oscillator on the temperature. Such a relatively inaccurate temperature value may be reasonably accurate for controlling processes, where the tolerances are large. For example in processes that include cooling steps, the objects may enter subsequent step after they have been cooled enough. In some cases it may be possible to determine the limit even without calibration. Moreover, if calibration is not used, the measured value {f'osc) may be used for decision making instead of the determined approximate value of the environment variable ( T). It has been found, that without calibration, temperature can be measured using some remote access appa- ratuses with an accuracy of 1 0 - 20 °C, while after a second degree calibration an accuracy of about 1 °C may be obtainable. In case a set of remote apparatuses is calibrated, it is possible to form calibration data such that part of the calibration data concerns a set of remote- access apparatuses and part of the data concerns the individual apparatus. For example if the calibration measurements are be done for a set of remote- access apparatuses, the calibration data thus obtained will be applicable to the set of remote access apparatuses. However, calibration data may also comprise correction terms for individual remote-access apparatuses. For example, the coefficients of the first degree polynomial, a or b, may be the same for all remote-access apparatuses having an RFID chip of the same family, but in addition, calibration data may comprise a correction term a'o or b'o indicative of the offset of the individual remote-access apparatus in relation to the set of apparatuses. Thus, for example, the temperature for an individual remote-access apparatus could be determined as

Here only the correction term b'o needs to be known for each individual remote-access apparatus, while the coefficients bi and b ₀ may be found from calibration measurements of a set of remote-access apparatuses, and are therefore applicable to a set of remote access apparatuses. This allows, for example, a remote-access apparatus to contain information indicative of the correction term, and a reader device to contain information of the other coefficients. Alternatively, a remote-access apparatus may contain the value of the constant term, i.e. bo ₊ b'o, while the information on the slope bi may be stored in a reader device. Thus, the calibration data may be divided to at least two parts, and the parts may be stored on different storage devices. Therefore, the memory requirements for the remote-access apparatus are relatively small. Moreover, some typical values for the correction term may be coded in a table so that these values can be pointed with a piece of data that is stored in the tag. The tag may, as an example, contain a 8-bit integer, which is indicative of the value of the correction term. The reader device can then deduce the coefficient based on the RFID chip family, and obtain a value for the constant from a table using this 8-bit integer. Naturally, also for the coefficient bi or other coefficients, a correction term can be stored instead of the actual data. The calibration data may be stored as AFD in the remote access device, or it may be stored as AFD in another remote access device. Furthermore, the calibration data may be stored in the RFID reader device, in a detachable memory card used in connection with the reader device, in an external server, or the data may be stored partly in some or all of the previous, including the remote access apparatuses. For example, a correction term may be stored on the remote-access apparatus, while the other calibration data may be stored in the reader device, or in a server arranged to communicate with the reader device.

In order to store the calibration data, the calibration data may be sent to the corresponding device. For example, an RFID reader device, equipped to directly measure or receive information on the value of the environment variable, may form the calibration data, and send it or part of it to a remote access device or several remote access devices, an information server, or it may even send it to a storage part of itself, such as a memory chip or a memory card, for information storing purposes. Once formed and stored, the calibration data may be sold, e.g. on a memory card or from an internet server.

Some aspects of calibration are the functional form of g(T) or h(f) and the calibration points 7 ^" ,. Generally the dependence between the temperature and the oscillator frequency is not linear. However, to some accuracy, the relationship can be estimated to be linear in some cases.

Also generally, the frequency of the oscillator decreases as the temperature increases. Thus a first or second degree polynomial may suit well for the purpose in case the frequency of local oscillator is used to indirectly measure the temperature. As for the calibration temperatures, calibration measurements are preferably made during a typical life cycle of the remote-access apparatus, i.e. not as separate measurements in a laboratory, where calibra- tion measurements are often done. For calibration, several different calibration points should be used, and in case of temperature, measurements should be done in several different temperatures. Some points for calibration measurements may be available when testing the RFID chips, when bonding the chips to the substrate to form the inlay, when manufacturing an RFID tag using the inlay, or afterwards while using the remote-access apparatus. To describe some embodiments of the calibration process, one needs to under- stand the RFID chip manufacturing process, the chip-to-substrate bonding process, and the tag manufacturing process. For economical purposes one efficient way is to find and use useful calibration points from the normal life cycle of a remote-access apparatus. In contrast, calibration measurements could be done in a laboratory or an office, but this would require separate calibration steps in the manufacturing process. In case calibration process can be integrated in normal life cycle of a remote-access device, time may be saved. The life cycle may comprise manufacturing, transportation, and commercial use, as an example. The device for performing calibration mea- surement may be a handheld reader device or, or it may be an integral part of some apparatus used to handle good or other objects comprising remote-control apparatuses. It may be possible to measure the temperature and the frequency of local oscillator at the same time from several remote-access apparatuses. In particular, the reader device may be an integral part of at least one of the following: a platform for objects, a pallet for objects, a vehicle, a shelf in a warehouse, a forklift used in the warehouse, a shelf in a store, a bonding apparatus, an oven, or a reflow oven, and a temperature sensor may be arranged in connection with the reader device in order to send the reference tem- perature value to the reader device.

Typically the measurements are more accurate in case the value of the environment variable is interpolated, than when it needs to be extrapolated. Thus, the at least one value of the environment variable used in calibration mea- surements should be larger than what is expected in typical measurements, and at least one value of the environment variable used in calibration measurements should be smaller than what is expected in typical measurements.

When manufacturing tags, one step in the process is the bonding of an RFID chip to a substrate. Typically the chip may be solder-bonded to the substrate, or bonded with an adhesive, such as non-conductive, anisotropically conductive or isotropically conductive adhesive. Both solder-bonding and adhesive- bonding are bonding processes. For remote-access apparatuses, it is more common to use adhesive bonding, but in principle also solder bonding is possible. In case the chip is solder-boned to substrate, the chip is heated above the melting point of the solder and the solder melts. The input and output pads of the chip are usually bumped with bumps of solder before the chip is heated. The chip is the made in contact with the substrate such that the melt solder forms a galvanic contact with the substrate. Thereafter the chip and the substrate are allowed to cool below the solidifying temperature of the solder. Common solder include the Sn-Pb, Au-Sn, Bi-Sn and In-Sn. The melting points of these solders are approximately 1 83 °C, 280 °C, 1 38 °C, 1 1 8 °C, and the melting point may slightly differ from the solidifying point. Also the ternary Sn-Ag-Cu with the melting point of 21 7 °C is becoming increasingly popular. Also other than eutectic/ternary mixtures may be used, and other solders, as well. As soon as the chip forms a galvanic contact with the substrate, the RFI D tag may be operated. Thus calibration measurements can be made at the solidifying temperature of the solder and also during cooling. After the bonding process the tags are typically cooled to room temperature in a post-bonding cooling process. Therefore, in a solder-bonding process environment, the temperature is around 100 - 300 °C, and it may be possible to make calibration measurements in this temperature range. In the post-bonding process environment, the temperature decreases from around 200 °C to around 20 °C, and calibration measurements for the remote- access devices can be made in this temperature range. The post-bonding cooling process may last some minutes, which is a relatively short time. Temperature of the remote-access apparatus can be measured e.g. by using an thermal imaging camera capable of determining temperature based on the radiation. In case the post bonding process is much slower, a thermometer for measuring the ambient temperature could be used, since the process could be assumed stationary. However, a slow cooling process is not economical. Alternatively to measuring the temperature, one can measure only the frequencies as a function of time t, i.e. the measure the values {f' _osc ;t'i), and only later provide the information on the temperature at those instances, i.e. the pairs (t , T'j).

In case an adhesive is used to bond the chip to the substrate, pressure or temperature or both may need to be applied to chip to form a contact or to cure the adhesive. The system is kept in these conditions for a period of a curing time. In addition, the temperature of the chip may be initially raised to a pre-bonding temperature. In some cases, an electric contact may be formed already in the pre-bonding process, and in such case, calibration measurements may be done in the pre-bonding process. In case only temperature is applied, calibration data may be measured as described above. In case both temperature and pressure are applied, and the measured quantity is only weakly dependent on pressure, calibration data on temperature may be measured. In case pressure is applied, and pressure changes the measured quantity, calibration data for pressure measurements may be obtained. Calibration measurements may in some cases also be done between the pre-bonding and adhesive-bonding processes. The phase between pre-bonding and bonding is called bonding transition phase. In the bonding transition phase, the temperature of the RFID inlay is relatively high, and no pressure is applied. Typical pre-bonding temperature for adhesives are in the range of 70-90 °C, typical adhesive-bonding temperatures in the range of 150-230 °C, typical bonding pressures in the range of 100 kPa - 100 MPa, and typical curing time 5 - 30 s. After bonding, in the post-bonding process the remote-access device is cooled to room temperature. The post- bonding cooling process may last about 15 - 20 s, which is a relatively short time. Temperature of the remote-access apparatus can be measured e.g. by using an thermal imaging camera capable of determining temperature based on the radiation. Therefore, several measurements may be made during the cooling period in the approximate range of 20 °C - 230 °C. Moreover, since the temperature decreases exponentially to room ambient temperature, more calibration measurements are made close to room temperature than in higher temperatures, in case a constant time delay between calibration measurements is used. Temperature of the remote-access apparatus can be measured e.g. by using an thermal imaging camera capable of determining temperature based on the radiation. By a thermal image camera, the temperature of multiple remote-access apparatuses may be determined from one image. Typically, the thermal image camera may take a picture of the web, on which the inlays lie, and from the color of the RFID chips, the temperature of each RFID chip may be determined. Therefore calibration measurement of several RFID inlays in several temperatures during the cooling process. Even if this process takes about 15 - 20 s, it is emphasized, that these calibration measurements do not slow down the manufacturing process. In case the post bonding process is much slower, a thermometer for measuring the ambient temperature could be used, since the process could be assumed stationary. Moreover, a thermocouple may be bonded to a RFID chip to monitor the temperature during bonding, pre-bonding or post-bonding process. However, a slow cooling process is not economical. In some cases a reasonably accurate calibration may be obtained by assuming a known temperature decrement in the cooling phase, which information may have been obtained from previous measurements. Calibration data may be obtained from the measured pairs {f' _osc ;T ). Alternatively, the values f' _osc and T'i may be measured at certain instances ί',- of time, and calibration data may be formed by combining these partial calibration data.

Both solder and adhesive bonding may be done as a reel-to-reel process. In such a process, a large number of flexible substrates is stored on a reel. The substrates may form a matrix, i.e. several substrates may be located in the reel in rows and in columns. When the RFI D chip are bonded to the substrates to form the inlays, the reel is unwound, and the chips are bonded to the substrates. Finally the bonded inlays be winded to a roll. The bonding process may be preceded by a pre-bonding step. This process is schematically shown in Figs. 8b and 8c.

Fig 8b is a side view of a reel-to-reel bonding process. The substrates, which comprise the antenna, are manufactured, e.g. on a matrix form, on a web 860. The web is stored on a first reel 850. When the RFI D chips 871 , 872, 873 are bonded to the substrates, the first reel is unwound. The direction of rotation of the reel is shown with an arrow. As the web advances, the substrates enter first a pre-bonding area A, in which the RFI D chips 871 are attached to the substrate, and some pre-bonding pressure and temperature may be applied 880 to chip. In the pre-bonding stage some adhesive may be applied in between the chip and the substrate. Next the substrates with the pre-bonded chip arrive to bonding phase B. There the bonding pressure and temperature are applied 882 to the chip. The chips are in the bonding transition phase, when moving from the pre-bonding phase A to the bonding phase B. Finally the inlays enter the post-bonding cooling phase C. Chips in this area are shown with the number 873. Typically in the post-bonding phase no pressure or temperature is being applied; only the normal room temperature and pressure affect the inlays. The different phases are separated with dotted lines 890. In the solder-bonding process the pre-bonding phase is not needed. Figure 8c is a top view of the web and the chips. The width of the web, w, may be, as an example, about 200 - 500 mm, while the width of a substrate may be, as an example, about 20 - 150 mm, depending on the substrate and its orientation of the web. As an example, the size of the RFID chip may be around 0.5 - 1 mm in all three dimensions.

Fig. 9 shows a system for manufacturing tags. The chips 915 for the tags may be manufactured and/or programmed by one entity 910. In this entity, a silicon wafer comprising multiple RFID chips is processed. Typically the chips (i.e. dies) are tested with probes to find out, which chips are known to be good (known-good-die, KGD). These probes are typically part of a probe station, and the probes may form an electrically conductive path through the input/output pads of the dies, from the probe station to the dies. It may be possible, to measure the quantity as a function of the environment variable already on wafer level, i.e. after manufacturing the wafer, but before sawing the wafer into chips. If might be possible to do these calibration measurements also after the sawing process, i.e. for single dies. Therefore, some calibration measurement may be may in the chip factory, in the wafer- handling environment, and some calibration measurements may be done in the chip factory, in the chip-handling environment.

The antennas and the protective layers, e.g. the substrate, 925 may be manufactured by one or more other entities 920. The different elements making up a tag may be then combined to form a tag 930 or an inlay e.g. by bonding the chip to the substrate and possibly attaching a tag preform. The bonding process was discussed in more detail above. At the time of combining or at a different time, the properties tag may be measured at 940, for example to form advanced functionality data AFD to be stored into the tag memory. For example, the tag's temperature measurement capability may be calibrated and the calibration information may be stored into the tag memory. For example, the calibration coefficients may be stored in a kill password area of the tag. This may happen at any phase, e.g. during or after chip manufacturing, during or after combining the tag, or during printing (conver- sion), or in a completely separate phase. The tag may then be printed 950 at a facility where the tag is taken into use. The advanced functionality code AFC indicating the tag type and allowed operations, as well as the advanced functionality data AFD may be stored to the memory of the tag at this point, or the storing may happen at an earlier phase. The result of this process is a tag 960 with advanced functionality capability indicated by an AFC and supported by advanced functionality data AFD in the memory. The system in Fig. 9 may be implemented in a single facility by a single operator, or the different elements may be carried out at different locations.

Measurements may also be used to determine the functionality of the remote-access apparatus. For example, in case remote access apparatuses are designed to be used to determine the temperature using previously determined calibration data for a set of remote apparatuses, measurements may be used to determine the error of the determined temperature for a specific remote-access apparatuses by comparing the determined temperature to a measured reference temperature. I.e. in the measurement one may find out that for some reason a remote-access apparatus does not function as designed, and may thereafter be thrown away. This is preferably done in the remote-access apparatuses' life cycle as early as possible, in order to avoid accumulating costs. Such measurements may be done e.g. after the RFID inlay comprising the chip and the substrate has been manufactured.

When the chip is bonded to the substrate, the inlay is formed. To make up an RFID tag or other remote-access apparatus, the inlay may be attached a tag perform or other object. Some calibration measurement may also be done while manufacturing the tag. Temperatures in this process are typically close to room temperature.

After the tag manufacturing process, the remote-access device is brought into service. Typical application of remote-access apparatuses are in logistics and commerce. A transportation vehicle may comprise a reader device that is configured to make calibration measurements. Therefore, some calibration measurements may be done in the vehicle. Naturally, also other measurements can be done in the vehicle during transportation. It should be emphasized, that measurements of the value of the quantity can be made even if the remote-access apparatuses are not calibrated. After the transportation, the remote-access devices might be located in a store, i.e. warehouse or a commercial store. A reader device may be installed in the store to make cali- bration measurements or other measurements. In order to be able to make calibration measurements, the value of the environment variable needs to be known from other, direct, measurements. It may be possible to form calibration data in these locations, i.e. perform calibration measurements as dis- cussed above. In some cases, e.g. if the temperature of a warehouse is stabilized, it may be possible to form partial calibration data based on location information. Denoting the location by r, it may be possible that partial calibration information comprises the measured values of the quantity and the variable r, i.e. { f'osc ), and since the temperature of the warehouse is stabilized, the other partial calibration information ( T',r) is known. In case the remote- access apparatus travel through a number of places, the location information, r, may possible be stored as information indicative of the location, in which the calibration measurement was done, such an integer number corresponding to a specific warehouse.

Calibration can be done either incrementally or in a single run, and also only partial calibration data can be measured. In an incremental calibration, the reader device requests old calibration data and measures the value of the quantity using a remote-access apparatus. The old calibration data can be stored in the remote-access apparatus, the reader, a memory card or in a external server. The reader device then uses this information to generate new, possibly more accurate, calibration data. New data may comprise the measured value and the time or location of measurement, or the new data may comprise the measured value and the corresponding value of the envi- ronment variable. Furthermore the new data may comprise, when applicable, any or several of: the identity of the remote-access device, the time, the location, and the value of the environment variable. In order to be stored, the new calibration data is sent. It may be sent to the remote-access apparatus, to another remote-access apparatus,_the memory of the reader device, a memory card, or an external server, or to many of the previous. Furthermore, different parts of the new data may be sent to different entities. The existing calibration information may be e.g. all the measured {fOscfJ ;ΤΊ) triplets, and the new calibration information may be this with an added, most recent triplet. Some calibration data may also be removed. It is also possible to weigh the calibration measurements such that the recent calibration measurement results are give more weight than the older results. Thus, in the determination of the value of the environment variable, the most recent known values are given more weight than the older values. Moreover, it is possible to weight the calibration measurement results such that more weight is given to measurements that are done near the probable use conditions. E.g. more weight can be given to measurements near the room temperature than to measurements near the bonding temperature. Apart from calibration measurements, measurements may be formed using only the old calibrations data. In this case the new calibration data is not formed. When calibration is done in a single run, several values of f' _osc and Γ, are measured, and calibration data generated based on these measurements. The calibration data may be stored as AFD in the remote-access device or another remote-access device, in the RFI D reader device, in an external server, or the data may be stored partly in some or all of the previous. More- over, a tag may contain the calibration data of another tag or the calibration data of several other tags.

Calibration can be done based on partial calibration data, when in the calibration measurements the values f' _osc and times t or locations r, are stored. The remote-access device, the RFI D reader device, or an external server, or any combination of these, may be used to store the data. Separately from these measurements, the calibration temperatures T at these times or in these locations are measured. It is also possible, that the temperatures are not measured exactly at the times t . In such case the temperature can be measured at different times, and linear or other interpolation technique(s) may be used to deduce the temperature at the times t . These results may also be stored to a remote-access apparatus, an RFID reader device, a memory card, an external server, or any combination of these. By using the corresponding times or locations, the values of the measured quantity can be associated with the values of the environment variable to obtain the data points {f' ₀ sc,i ^' , T'j) or the representative data points. In case calibration is done on environment variable, after sufficient amount of calibration measurements, the coefficients a or b or some other calibration data may stored as AFD in the remote access device, on a memory card, in the RFID reader device, in an external server, or in any combination of the previous. In case the same coefficients are used for a set of remote-access apparatuses, a single measurement can reveal an estimate for the correction term b' ₀ .

The calibration data can be used to determine the value of the environment variable based on a measured quantity. For example, once calibrated, the temperature of a remote-access apparatus can be determined based on the frequency of the local oscillator. This information can be used e.g. to show the temperature on reader device's display or on the tag's display. The value of the environment variable is often needed at the time the measurement is made, i.e. the calibration can be preferably be done before the measurements. However, the measurable quantity, such as the frequency, can be measured even without calibration. Therefore, this quantity of a remote- access device can be measured first in a first environment, e.g. during transportation, without correlating it with the environment variable. The values of the quantity may be stored e.g. on the remote-access device or an external server. Furthermore, if needed, after the transportation temperature during transportation can be deduced using calibration data. The temperatures can be deduced much later or in another environment, an analysis environment, such as an office or a laboratory. The measured values of the measureable quantity can be provided for the analysis over an interface, for example on internet interface, an interface of the reader device or by using a memory card as the interface. This also means that the reader device may be transferable in relation to the device, where the data is analyzed. The calibration data, if calibration has been done for the corresponding chip family or the corresponding remote-access device, may be obtained from a server, or ordered on a memory card, after the transportation. The information may also be priced, and used only on need-to-know basis. Alternatively, the tag from the interesting transportation together with the frequency measurement results can be later sent to a service provider for making calibration mea- surements and doing analysis to determine the temperatures during transportation. The frequency measurement results may have been stored on the device itself, or they may have been stored on a server, memory card, or the reader device. Moreover, a re-calibration may be done for a tag that has been in use for some time. Also, an already calibrated first remote-access device can be used to make calibration measurements. That is, once the first remote- access device has been calibrated, it can be used to make accurate measurements of the environment variable. Therefore, when calibrating a second remote access device, a reader device may determine the value of the envi- ronment variable using the first remote access device, and to generate calibration data regarding the second remote access device, also measure the value of the measurable quantity from the second remote access device. Calibration data regarding the second remote access device can then be generated as discussed above.

Fig. 10 shows a method for manufacturing tags with application data stored in a password memory. Some of all of the method steps may be carried out by a single entity, or the steps may be carried out by different entities. At phase 1010, the chip for the tag is manufactured so that it can provide an advanced functionality. At this phase it may be possible to do calibration measurement using probes, as discussed earlier. At phase 1020, the chip is programmed, e.g. to contain program code and data for providing advanced functionality. At this phase, password areas on the chip may also be programmed, e.g. to contain application data such as calibration information. At phase 1030, the antenna and the protective layer are manufactured. At phase 1040, the antenna and the protective layer are combined with the chip to form a tag or an inlay. Calibration measurements at several relatively high temperatures may be made during the bonding process or in the post- bonding cooling process, since many bonding processes require high temperature or high pressure or both. At this phase, password or other memory areas on the tag may also be programmed, e.g. to contain application data such as calibration information. It is to be noted that for so-called passive tags, there will not be an energy source on the tag, that is, they will be energetically essentially passive. The tags will draw their energy essen- tially from the read-out signal, as explained earlier. At phase 1050, the properties of the tag may be measured for storing onto the tag or to be kept in a database for later access based on the tag identification. At this point calibration measurements can be performed also in low temperatures. It is possible to make calibration measurements also in high temperature at this point, in case they were not made during the bonding process. For example, calibration information may be determined and password areas on the chip may be programmed, e.g. to contain application data such as calibration information. At phase 1060, the tag may be printed, that is, the tag may receive information such as an electronic product code. At this phase, password areas on the tag may also be programmed, e.g. to contain application data such as calibration information. At phases 1040, 1050 and 1060, the tag may also receive advanced functionality data and an advanced functionality code. Password fields may be employed in this storing.

Figure 10b shows some phases of a life cycle of a remote-access apparatus. The wafer 1070 comprising RFID chips 1074 is manufactured in a wafer factory. After the wafer has been manufactured, it is sawed to RFID chips. A wafer may comprise tens of thousands of RFID chips; a large 12-inch wafer may comprise a hundred thousand chips. Calibration measurements may be performed for the wafer of for the chips. The substrate 1076 comprising a film 1072 is made by processing a conductive wiring onto the film. A chip is bonded to a substrate to make up an RFID inlay 1078. Bonding process in itself has several points, in which calibration can be done, as discussed above. The inlay is attached to a tag perform 1080 to make an RFID tag 1082 or a remote-access device. The tag 1082 may be attached to a product 1084 to make up a traceable product 1085. Several of such objects may be packed on to a pallet 1086. For transportation, such pallets 1086, 1088 may be loaded into a vehicle 1090. Finally, the pallets are transported to a warehouse 1092 or a store 1094. The pallet may also be transported from a warehouse to a store. Other points for making calibration measurements include right after packing, e.g. when the products are on the pallet. The pallet itself may include a calibration device. Furthermore, a calibration device may be located or integrated in the vehicle 1090, and calibration measurements may be done during transportation. The pallets are transported to a warehouse or directly to a store. In the store, the pallets are unpacked, and the products are made for sale. Both the warehouse and the store may include natural places or devices for calibration measurements, such as shelves, forklifts, carts, or conveyor belts. Naturally, these phases can also be used to monitor the value of the environment variable, if calibration has been performed. In addition, these phases can be used to record values for the measurable quantity, and later determine the corresponding temperatures by using calibration data. Furthermore, some of these phases can be used to record values for the measurable quantity, and later combine the results with the corresponding value of the environment variable to form calibration data. Information on time or location may be used to associate the corresponding variables.

Furthermore, quality control may reveal in any phase of the life cycle that the item has become unusable. Therefore, it may be possible to send the remote-access apparatus for calibration after the fault has been noticed. In an embodiment, the values of the measurable quantity are measured without calibration, and only when the quality controls reveals a fault, the remote access apparatus is calibrated, and the recorded raw data is used to solve the value of the environment variable, e.g. the temperature, in which the item has been. Various operators in the life cycle may also offer calibration services during their operations. For example, a transporter may offer transportation in a accurately controlled temperature. Therefore calibration data can be obtained during transportation. Moreover, if several data points are needed, the transporter may offer transportation in several given temperatures for a given time, e.g. the temperature can be kept at 1 , 3, and 5 degrees C for a given period of time during transportation. Similarly, the warehouse or parts of the warehouse can be equipped with accurate temperature control for performing calibration measurement in the warehouse. Furthermore, the items may be stored in such a warehouse before transportation as single items or on pallets (not shown in Fig. 10b) .

Fig. 10c illustrates the processes of collecting raw data and calibration data and their combination to obtain temperature values. In Fig. 10c the life cycle of the remote access apparatus, as shown in Fig. 10b from the wafer 1070 to the store 1094 or warehouse 1092, is reproduced in the middle. The evolution of time is shown with the arrow 1061 . During the life cycle, raw data 1062 may be collected. The collection of raw data is represented with arrows 1063. Raw data comprises a value of the measurable quantity and may comprise the identity of a remote access apparatus associated with the value. Raw data may also comprise also information indicative of time and/or location is which raw data was measured. Raw data may comprise several values of measurable quantity associated with the identity of the remote access apparatus. It may also comprise information indicative of time and/or location the measurements. Furthermore, raw data may comprise the said information for a second remote access apparatus or a multiple of remote access appara- tuses. Raw data may be stored for example to the remote-access apparatus, another remote access apparatus, internal memory of a reader device, a detachable memory card on the device, or an external information server. In addition to raw data 1062, calibration data 1064 may be collected during the life cycle of the remote access apparatus. The collection of calibration data is shown with the arrows 1065. The calibration data comprises also reference values for the value of the environment variable, e.g. temperature. Calibration data may be collected as partial calibration data, which are later combined to form calibration data. For example, the frequency of local oscillator as function time may be measured with a first data logger, and the temperature as a function of time with a second data logger. These data may be combined to produce calibration data. As soon as calibration data is formed and raw data measured, raw data may be sent 1056 and calibration data may be sent 1067 to determine 1068 the value of the environment variable, e.g. temperature. In an embodiment, calibration data is measured first, and raw data may be converted to a temperature value as soon as it is measured. For example, if the temperature of an item is to be measured, data regarding the item can be measured only after the remote access apparatus has been attached to the item 1085. However, calibration data may be measured form the wafer 1070, chips 1074, the inlay 1078, or from the tag 1080, e.g. in the bonding process (Fig. 10c "bond"). In another embodiment, raw data is measured first, and calibration data is measured only when needed. In Fig. 10c this is depicted with the label "calibrate (post-use)", meaning that some remote access apparatuses may be sent for calibration after the typical use, e.g. because quality control reveals a reduced quality for the item. Then the information regarding the environment for the item can be determined afterwards. Raw data can be stored on a device and it may be accessible over an interface. In an embodiment, the calibration data forms a database that comprises the identity of at least one remote access apparatus and the calibration data associated with that remote access apparatus. In a preferred embodiment, the database comprises calibration data of several remote access appara- tuses associated with the corresponding identity. Then, when the raw data comprises the identity of the remote access apparatus and a value of a measurable quantity, this calibration database can be used to determine the corresponding temperature. The database can be used e.g. such that the both the value f _0S c' of the measurable quantity and the identity of the remote access apparatus is received from the remote access apparatus. Using this identity, the corresponding calibration data may be obtained from the database. Finally, using the obtained calibration data and a value f _0SC Of the measurable quantity the temperature T may be obtained, e.g. using a function h such that T'=h(fosc').

The database can also be distributed. For example a part of the database can be stored in an external database, a part in a remote access apparatus, and a part in the reader device. Furthermore, the database can be distributed to several remote access apparatuses. In case the calibration data is stored to the remote-access apparatus that is used for measurements, the identity of the remote-access apparatus is not necessarily needed to obtain calibration data.

Information from the database can be given or sold to a user on allowed to know basis. For example, calibration data regarding a remote access apparatuses for a chip family can be cheap, while the more accurate calibration data concerning a specific remote access apparatus can be more expensive. Most accurate data calibration data obtained in laboratory conditions after a decrement in quality has been observed may be provided as a service, and may be even more expensive. The calibration database can be updated by doing calibration measurements and storing the identity of a remote access apparatus together with the corresponding calibration data to the database. In an embodiment, the database is distributed to remote-access apparatuses such that each apparatus comprises its calibration data. Thus, in an embo- diment, the identity is not stored. Initially an empty database may be formed without measurements, and the first calibration data may be added to the empty database.

Moreover, the database can be made accessible for a user only with an access code. Thus, only authorized users may have access to the database. The access code may be indicative of the access type: The database user may have full access, i.e. read and write access, to the database, a user may have full read access to the database, i.e. the user may read the calibration data of a single remote access apparatus from database, or a user may have limited read access to the database, i.e. the user may only obtain some statistical values of the calibration data such as mean values of the parameters of a function, the mean regarding e.g. a chip family.

When determining the value of the environment variable, calibration data is needed. Calibration data can be requested from an entity, and the entity may be a database comprising calibration data, or it may be a service provider that performs the calibration measurements by request and deduces the calibration data based on those measurements. In an embodiment, the raw data measured with a remote-access apparatus and the corresponding remote- access apparatus may be sent to a service provider to determine the corresponding values of the environment variable, e.g. temperature. In this case, the service provider receives the raw data, and may request calibration data either from a database or from a calibration data measuring device, i.e. calibration device. The calibration device may comprise an RFID reader device and means to measure a reference temperature, and may send e.g. the data points of calibration measurements or the parameters of a calibration function to the service provider. The service provider may then determine the value of the environment variable using the raw data on the calibration data. Fig. 1 1 shows temperature measurement arrangement as an illustration of utilizing memory capabilities of a tag according to embodiments of the invention. At phase 1 1 10, the reader may request the tag to send an advanced functionality code AFC to indicate that the tag is capable of being used in a temperature measurement. In response to this request at phase 1 1 15, or in response to a standard request, the tag may send an advanced functionality code AFC to indicate the type of the tag and the capabilities of the tag. For example, the AFC may indicate how accurate the temperature measurement with this tag may be. As explained earlier, the reader may at phase 1 130 then request at least one value a directly measurable property, such as the backscattering frequency, from the remote-access device. Using this at least one value, the reader device may determine a value of the measurable quantity, such as the frequency of the local oscillator or the TRcal value of the point where the backscattering frequency changes. The steps 1 130 and 1 135 may be repeated as necessary. Using the received information, the reader may alone or with the help of the system determine the tag tempera- ture based on knowledge of the local oscillator properties and the functionality of the tag. The local oscillator frequency changes with temperature, and this affects the oscillator information.

At phase 1 140, the reader may then send an access password to the tag to gain access to application data e.g. stored at least partially in another password such as the kill password. The application data may comprise the calibration data, part of the calibration data, partial calibration data, or a part of partial calibration data. The tag may allow access to the requested information at phase 1 145. In phase 1 150, the reader may then send a read request to the tag to read the password e.g. to read the kill password of a tag. It needs to be noticed here that sending the kill password from the reader to the tag would cause the tag to become inactive, but reading the kill password may be safe in this sense. Since access has been granted to read the kill password, the tag may send the kill password to the reader in phase 1 160. The (kill) password may contain as such or in encoded form some application data, e.g. calibration data for determining a temperature of the tag. It needs to be understood that some of this information may also reside in the system e.g. in a database as explained earlier. When the reader or the system has received the data contained in the kill password, the received password may be converted to calibration data (e.g. coefficients for converting the oscillator data to a temperature value) in phase 1 160. A temperature may then be determined by using the oscillator information and the calibration data, and possibly some other data. An embodiment for calibrating a remote-access device is depicted in figure 1 2. Calibration is suitable for remote-access apparatuses with advanced functionality, but in some cases, it may be possible to measure the quantity from an RFID tag even without requesting an advanced functionality code of the remote-access device. In some embodiments the reader device may communicate with the remote-access device to determine whether the remote-access device is capable of sending advanced functionality information, as shown in Fig. 1 1 . For clarity, this step is not shown in Figs. 12-1 5. After this step, the reader may measure at least one value of a directly measurable property, such as the backscattering frequency. When enough of these values are measured, the value of the measurable quantity is deter- mined without calibration information, i.e. the value of the measurable quantity becomes measured. For example, the frequency of local oscillator may be measured using the information on two backscattering frequencies. All these phases are shown as a single step 1215. Once the oscillator frequency, or the value of another measurable property, is determined, it can be used to calibrate the device by calibration measurements, as discussed above.

As a result of calibration measurements one needs to obtain the data points (f'osc T'). As soon, as the value of the measurable quantity is determined, the value of the corresponding environment variable, e.g. temperature is determined. The value of this variable can be requested from an external sensor, 1 225, or from an internal sensor, 1 230, located in the reader. The internal sensor may be a temperature sensor measuring the ambient temperature, or it may be on thermal imaging camera configured to measure the temperature at the remote-access device, or devices, if several remote-access apparatuses are being calibrated. After the value of the environment variable is measured, the data point(s) is/are stored, 1 235. Data points can be stored in the reader or in an external device, such as the remote-access apparatus or an external serve. Data points can also be stored on a detachable memory card installed in the reader. Multiple measurements are done in order to obtain enough points for calibration. In general one may make at least the same number of measurements as there are unknowns in the calibration function. Preferably, one may make much more measurements to average out noise always present in measurements. When enough calibration measurements are done, calibration data is formed and sent 1245. Calibration data may be formed in the reader device, or it may be formed in any part of the system that can read the stored data points and is capable of making relatively simple computations. It may even be possible, that no computations are needed, e.g. in case the calibration data comprises only two data points. Calibration data may be sent to a remote-access apparatus 1250, an external server 1255, or to internal memory or a memory card of the reader device 1260. Moreover, one part of the data may be sent to one device, and another part to another device, or parts of the cali- bration data may be sent to all of the devices. It should be noted, that the remote-access apparatus receiving calibration data may be different from the remote-access apparatus that is being calibrated.

Figure 13. shows an embodiment for incremental calibration of a remote-access device. First, the measurable quantity is measured 1310. Thereafter, the old, existing calibration data is requested 1315 from a data storage. The storage can be a remote-access apparatus 1320, en external server 1325 or a memory of the reader device 1330, either an internal memory or a detachable memory card. Thereafter the old calibration data is received 1335, and a value for the environment variable is requested 1340. A sensor 1345 may provide the device with the value. The sensor may be located in a reader device, or may be an external sensor. Once the value of the environment variable is obtained, new calibration data is formed and sent 1350. The new cali- bration data may be sent to a data storage unit to be stored. The storage unit can be a remote-access apparatus 1355, en external server 1360 or a memory of the reader device 1365, either an internal memory or a detachable memory card. It is clear, that the steps measuring the quantity 1310, requesting the old calibration data 1315 and requesting the value of the environment variable 1340 may be done also in a different order. Moreover, it is clear, that the process is applicable also to form partial calibration data, if the value of the environmental variable is replaced with a value, such as time or position, which can later be used to associate this measurement to a particular value of the environment variable. Figure 1 4 shows schematically the process of measuring temperature using calibration data and a remote-access apparatus. As in Figs. 1 2 and 1 3, the measurable quantity first measured 1 420. To determine the temperature based on this value, calibration data is needed. Therefore, calibration data is being requested. Calibration data can be requested from the remote-access device 1 430, another remote-access device 1 435, the memory of the reader device 1 440, either an internal memory or a detachable memory card, or from an external server 1 445. Moreover, parts of the calibration data can be located in different entities. For example, the information server may contain the calibration parameters of the remote-access apparatus family, and the apparatus itself may contain a correction term. The different entities send the data to the reader, which receives the data, and determines the temperature using calibration data and the determined value of the measurable quantity 1 450. Finally, the temperature value is stored, or it may be displayed on a device 1 455.

Figure 1 5 shows schematically the process of measuring the frequency of a remote-access apparatus, and later determining the temperature corresponding to these measurements. As in Figs. 1 2 - 1 4, the measurable quantity is first measured 1 51 5. Thereafter the value is sent 1 520 to a storage device, which may be on the remote-access device, on another remote-access device, in the reader device as a memory chip or memory card, or elsewhere as an external storage unit. The storage unit receives and stores the data 1 525. In preferred embodiments, the information is stored in an external server or in the remote- access apparatus, such that it can relatively easily be requested later, if the actual temperature needs to be determined. This process is repeated until enough values are recorded. As an example, the fre- quency of the local oscillator in remote-access devices may be measured during transportation. Once enough values are stored, they can be used to determine the corresponding temperatures. For this purpose, calibration information is requested 1 535, and, if stored on an external device, also the measures values are requested 1 535. These pieces of data may be requested from different entities such as a remote-access apparatus 1 540, another remote access apparatus 1545, internal memory of a reader device 1 550, or an external information server 1 555. Moreover, parts of the calibration data may be located on different entities. In addition, it is possible that the calibration data does not exist. In this case the calibration data can be requested from a calibration service, which performs the calibration and send the data 1 557. As the calibration data and the stored values are received, the temperature during the frequency measurements can be determined 1 560. Finally a report may be put out 1 565. It should be noted, that the reader device in the steps 1 51 5, 1 520, and 1 530 is not neces- sarily the same device that is used to perform the analysis part, i.e. the steps 1 535, 1 560 and 1 565. Moreover, the measuring steps 1 51 5, 1520, and 1 530 may be done in a first environment, such as a transportation vehicle, a store or a warehouse, and the analysis steps 1 535, 1560, and 1 565 may be done in a second environment, e.g. in an office or a laboratory. Naturally, a calibration service manager can also provide the temperature values, if the measured values of the quantity are known to the calibration service manager. This embodiment may be applicable, if one wants to know, e.g. after a transportation, to what kind of temperatures the remote-access device was exposed.

What has been described above in the various embodiments regarding RFID tags is often implemented by a chip on the RFID tag. Therefore, one target of the invention is an RFID chip providing advanced functionality by RFID tags.

The present application has been filed together with the applications titled "Data storage on a remote-access apparatus", "A method for determining an environment dependent usability of an item", "Temperature monitoring system", "Temperature managed chain", all on the same date, and by the same applicant. For the purposes of storing and using application data in a password, the application "Data storage on a remote-access apparatus" is referred to. For the purposes of determining usability of an item, using thresholds and ranges for the same, and for statistical determination of usability, the application "A method for determining an environment dependent usability of an item" is referred to. For the purposes of determining temperature information in various systems, the application "Temperature monitoring system" is referred to. For the purposes of monitoring temperature of in a temperature-managed chain, the application "Temperature managed chain" is referred to. The various embodiments of the invention can be implemented with the help of computer program code that resides in a memory and causes the relevant apparatuses to carry out the invention. For example, a tag, a chip or a reader device may comprise circuitry and electronics for handling, receiving and transmitting data, computer program code in a memory, and a processor that, when running the computer program code, causes the reader device to carry out the features of an embodiment. Alternatively or in addition, a tag or a chip for a tag or a reader device may comprise logic circuitry for implementing the same functionality as may be carried out by means of program code run on a processor. Yet further, a network device may comprise circuitry and electronics for handling, receiving and transmitting data, computer program code in a memory, and a processor that, when running the computer program code, causes the network device to carry out the features of an embodiment. A system may comprise any number of tags of the same kind or different kinds, and reader devices and network computers in any combination.

It is clear that the present invention is not limited solely to the above-presented embodiments, but it can be modified within the scope of the appended claims.