FIELD OF INVENTION The present invention relates to a system and a method for passive Radio Frequency Identification (RFID) reader for reading tags of ultra high frequency (UHF).

BACKGROUND OF INVENTION Radio Frequency Identification (RFID) has been around for decades. It is generally said that RFID can be tracked way back to World War Il where the technology was used as radar to track incoming planes. The drawback was the planes can never be identified as a friend or foe. RFID has highly evolved since that day. Nowadays RFID are widely used all around the world for many applications, mainly for tracking and monitoring purposes. RFID can be categorized as a powerful emerging technology that enables companies to better track assets, tools and inventory, and many other applications, across every industry. In the tracking applications, either humans or animals can have a tag attached to them in order for the RFID reader to track. This RFID reader will track and read the information stored on the tag in a non-contact matter. Each tag will also have their own unique identification, thus preventing any collision that might happen amongst different tags.

Using an RFiD reader and tag, many applications can be developed. It may be used in attendance system where lecturers or conference conductors may easily track and store information regarding the absentees and attendees of one classroom or event. Other than that, the RFID reader and tag may be used to track staffs movements. This type of application is most likely being done in clinics or hospitals where the RFID technology can detect the presence of a certain doctor or medical staff in that area. It can also be applied to medical equipments or any other expensive equipment, in order to prevent loss of equipment. Each RFID reader and tag is classified into different groups. These groups are categorized based on how the readers and tags communicate, the type of frequency used and power sources. In communication type, it is either the active type or the passive type; frequencies would range in long-wave type, medium-wave type, short wave type, ultra short-wave type and microwave type. In terms of power, it is either the RFID tag uses its own power source or otherwise.

Passive types are much more likely to be applied to attendance system, gate system or any application that requires low-range distances. On the other hand, active types are much suitable for tracking and monitoring applications. This is because active types can provide longer distance tracking.

However, passive RFID tags have no power source of their own. As an RFID reader is at heart a radio transceiver which is a transmitter and a receiver that work together to communicate with a tag. As such, it faces the same challenges all radios encounter plus a few specialized problems unique to wireless communications. These challenges are such as accurate modulation of carrier frequency as well as signal distortion issues. Apart from these, power concerns are part of the problem as well as too much DC power should not be wasted. Therefore, there is a need in the field for a reader system that provides accurate signal modulation in a less power hungry manner and with as minimal distortion as possible. SUMMARY OF INVENTION

Accordingly there is provided a passive Radio Frequency Identification (RFID) reader system which reads tags of ultra-high frequency (UHF), characterized in that, the system includes at least one real time clock, at least one data storage means which is connectable to a data transfer means between a reader and a processing means, an input device, wherein the input device is used for data entry, a protocol converting means, wherein the protocol converting means is connectable from the reader to the processing means, a power management means, wherein the power management means provides power to the reader, a plurality of antennas, wherein the plurality of antennas communicate with at least one electronic tag by transmitting or receiving a radio frequency signal, wherein the real time clock keeps track of current time inside the reader and the power management means. There is also provided a method of reading tags of ultra high frequency (UHF) ₁ characterized in that, the method includes the steps of transmitting an unmodulated radio frequency (RF) carrier signal from a reader and modulating amplitude and/or phase of back-scattered RF carrier signal from a tag. The present invention consists of several novel features and a combination of parts hereinafter fully described and illustrated in the accompanying description and drawings, it being understood that various changes in the details may be made without departing from the scope of the invention or sacrificing any of the advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

Figure 1 illustrates a block diagram depicting the architecture of an embodiment of a passive RFID reader system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a system and a method for passive Radio Frequency Identification (RFID) reader for reading tags of ultra high frequency (UHF). Hereinafter, this specification will describe the present invention according to the preferred embodiments of the present invention. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims. The following detailed description of the preferred embodiments will now be described in accordance with the attached drawings, either individually or in combination. The present invention provides for a Radio Frequency Identification (RFID) reader system (200) to support all types of cards conforming to International Organization for Standardization (ISO 18000-6C). A passive Radio Frequency Identification (RFID) reader system (200) which reads tags of ultra-high frequency (UHF) is provided, as seen in Figure 1, which includes at least one real time clock (10), at least one data storage means (20,80) which is connectable to a data transfer means between a reader (70) and a processing means (90), an input device (30), wherein the input device (30) is used for data entry, a protocol converting means (60), wherein the protocol converting means (60) is connectable from the reader (70) to the processing means (90), a power management means (100), wherein the power management means provides power to the reader (70), a plurality of antennas, wherein the plurality of antennas communicate with at least one electronic tag by transmitting or receiving a radio frequency signal, wherein the real time clock (10) keeps track of current time inside the reader (70) and the power management means (100).

Referring to Figure 1, a real time clock (10) is a clock that keeps track of current time even when a computer is turned off and most often the clock (10) is in the form of an integrated circuit. Real-time clocks (10) run on a special battery that is not connected to a conventional power supply. This enables the system (200) to be free of time critical tasks while providing accuracy in timing. The real time clock (10) in this system (200) is advantageous in terms of tracking time and date of a reader (70). Tracking of time and date is essential in developing an application that requires safety and surveillance.

Referring to Figure 1 , a data storage means, such as a 32 kilobytes flash memory (20) is a non-volatile memory that can be electrically erased and programmed by a user. The flash memory (20) is used for general storage and transfer of data between computers and other digital products. As it is non-volatile, no power is needed to maintain data stored on its chip. The flash memory (20) also offers fast read access time that is critical for the application of RF tag reading. The flash memory (20) stores data processed by a processing means (90) such as a processor core (90) within the system (200) and a 32 kilobytes RAM (80). The flash memory (20) also functions as a backup system to store data safely during a power failure to be retrieved later.

As seen in Figure 1, a liquid crystal display (LCD) (40) is connectable to a processor core (90) wherein the LCD (40) used is an alphanumeric LCD with two lines of 16 characters display. An Recommended Standard 232 (RS232) com (50) is used for converting data from the reader (70) into serial binary before data transmission between the system (200) to an end user. The RS232 com (50) uses a 25 pin DB-25 or 9 pin DB-9 connector to connect to the RS232 com (50) and to a serial port of a processor core (90). Referring to Figure 1 again, a protocol converting means (60) such as a gateway module

(60) is used to convert RS232 protocol into TCP/IP. In this embodiment, the gateway module (60) used is an Ethernet coprocessor. The gateway module (60) enables remote gauging, managing and control of a device through network based on Ethernet and

TCP/IP by connecting existing equipment with RS232 serial interface. Therefore, the gateway module (60) transmits data sent by serial equipment as TCP/IP data type and converts back TCP/IP data received through network into serial data to transmit back to serial equipment. The gateway module (60) works to create a networking between end users' processors.

As seen in Figure 1, the RFID reader (70) is a Nano UHF single antenna reader. A backscattered signal is demodulated to baseband through standard in-phase quadrature (I/Q) mixer stage and is filtered and amplified. A baseband signal is then sampled and processed by a nano-controller. The RFID reader (70) is small with a low power consumption, such as a 2 milli Ampere (mA) average and at 5 Volts (V) during standby. The RFID reader (70) in this system (200) is a multiprotocol reader wherein the reader (70) operates at both European UHF frequencies band (865-868 MHz) and North American UHF frequencies (902-928 MHz). Programmable reader identification is available in this RFID reader (70) for networking many readers together. The RFID reader (70) also can be connected to an external antenna via a SubMiniature version A (SMA) connector or micro-miniature coaxial (MMCX) connector. As shown in Figure 1 , Random Access Memory (RAM) (80) is a type of data storage means (80) for a computer wherein the RAM (80) is in a form of integrated circuits that allow stored data to be accessed in any order. In this system (200), the 32 Kbytes RAM (80) is used. This RAM (80) is specifically used to assist the processor core (90) in order to handle the data storage and memory of the processor core (90). The system (200) uses a small 32 Kbytes RAM (80) based on a simple but multi-purpose application intended for the reader (70).

Referring to Figure 1, a power management means (100) is used as the power supply for the system (200) wherein an input supply of 9-12 V, 500 mA is used. Output of the power management means (100) is rated at 3V and 5V. The system (200) further includes a capacitor to store power in order to prevent the processor core (90) from losing data.

Additionally, a power supply converter is used to convert 230 V alternating current (ac) to

9 V direct current (dc) with 1000mA into the system (200) for a suitable voltage in the system (200).

RFID cable used in the system (200) is very important to the overall performance of the RFID reader system (200) implementation. If the cable is not a low loss cable and is not shielded properly, there will be interferences and lower read rates. If high quality ends are not used for both the reader (70) and the antenna connection, noise and potential line loss will appear in the read rate. Connectors are supplied as straight connector or 90° angled, depending on installation requirements. The cable is connected to 900MHz 8dBi Flat Patch Antenna which is a high gain flat patch antenna that provides 8 dB gain with broad coverage. The antenna is suitable for both indoor and outdoor wireless Local Area network (LAN) and wireless video applications in the 900MHz ISM band, GSM, 900MHz cellular and RFID applications.

All the information and stored data in tag will be transferred to the reader (70) and all data will be display on the LCD (40).

A method of reading tags of ultra high frequency (UHF) is provided wherein the method includes the steps of transmitting an unmodulated radio frequency (RF) carrier signal from a reader and modulating amplitude and/or phase of back-scattered RF carrier signal from a tag. The reader (70) has an antenna that emits radio waves, the tag responds by sending back its data. A number of factors can affect the distance at which a tag can be read. Frequency used for identification, antenna gain, orientation and polarization of the reader's (70) antenna and transponder antenna, as well as placement of the tag on the object to be identified will all have an impact on the system's (200) read range. Furthermore, an RF (radio frequency) field is generated, so that when the system (200) detects a tag, the received information is transferred to a main server through a provided network.

The tag receives both information and operating energy from the RF carrier signal. Tags are passive, meaning that they receive all of their operating energy from the reader's (70) RF waveform. A reader (70) receives information from a tag by transmitting a continuous- wave (CW) RF signal to the tag. Therefore the tag responds by modulating the reflection coefficient of patch antenna, thereby backscattering an information signal to the reader.

The reader (70) receives information from a tag by transmitting an un-modulated RF carrier and listening for a backscattered reply. Tags communicate information by backscatter-modulating the amplitude and/or phase of the RF carrier. The signal transmitted to the tag and receiving signal from the tag use one antenna, at the same frequency. As the transmitting signal needs to activate the tags at a distance, the transmitting power is far greater than received power. This will result in reduction of the time delays when transmitting the signal. As the same antenna is used, signal leakage will occur at the receiving path, and all devices in receiving reader will be temporarily disabled. Therefore, the transmitter and receiver will not clash in working progress every time a signal is transmitted. This has solved the problem by delivering accurately modulated carrier frequency of 902 MHz until 956 MHz. The signals are also delivered undistorted at a desired absolute output power without wasting too much DC power. Low spurious radiation which is the distortion of the transmitted signal can lead to radiation at frequencies outside the authorized bands which can potentially interfere with other users. The system (200) is able to turn of transmission when not in use to save power and avoid creating a large interfering signal to be turned back on quickly when it is required to be in use.

This invention is intended for, though not restricted to, the field of RFID reader-tag communication with UHF band (902 MHz - 956 MHz) in a networking system that is suitable for both indoor and outdoor wireless LAN and wireless video applications in the 900 MHz ISM band, GSM, 900 MHz cellular and RFID applications.