Wireless communication module comprising an integrated antenna

FIELD OF THE INVENTION

An aspect of the invention relates to a wireless communication module, which comprises an integrated circuit that is provided with an antenna. The wireless communication module may transmit, or receive, a radiofrequency signal in a millimeter wavelength band via the antenna that is present on the integrated circuit. The radiofrequency signal may have a frequency of, for example, 60 GHz. The integrated circuit may be manufactured in, for example, CMOS technology. Other aspects of the invention relate to a data-handling apparatus that comprises a wireless communication module, an integrated circuit that is provided with an antenna, and a method of manufacturing such an integrated circuit.

BACKGROUND ART

Wireless communication in a millimeter wavelength band around, for example, 60 GHz, has several interesting features. A wireless transmission path, which extends between a transmitter and a receiver, exhibits a relatively high loss per unit of length in the millimeter wavelength band. This is due to absorption by oxygen and obstructions, such as walls. Although the relatively high loss per unit of length precludes long-range communications in the millimeter wavelength band, there are several advantages associated with this relatively high loss.

One advantage is that a wireless communication in the millimeter wavelength band is relatively secure. Since a wall will typically attenuate a radiofrequency signal in this band to relatively large extent, the wireless communication will be difficult to intercept in a room next door. It may even be impossible to intercept the wireless communication in the room next door. This property also allows an extensive frequency reuse on a premise: an individual wireless communication can take place in each room at the same frequency of, for example 60 GHz, without mutual interference.

Another interesting feature of wireless communication in the millimeter wavelength band relates to bandwidth. It is typically easier to achieve a relatively large bandwidth of, for example, 1 GHz, in the millimeter wavelength band than in a centimeter wavelength band. This is particularly true for antennas.

The aforementioned features make the millimeter wavelength band particularly suited for short-range wireless communications at high data rates. Such a wireless communication may effectively replace a high-speed data cable having a length in the order of, for example, a few decimeters or a few meters. Another interesting feature of wireless communication in the millimeter wavelength band is that antennas are sufficiently small to be formed on an integrated circuit. Accordingly, a single chip may comprise receiver circuits, or transmitter circuits, or both, as well as one or more antennas, which are coupled to the circuits. There is no need for a radio frequency coupling path between an integrated circuit, which comprises the aforementioned circuits, and an external antenna. Such a radio frequency coupling path is relatively expensive, as well as the external antenna. Accordingly, the millimeter wavelength band offers possibilities for relatively inexpensive single-chip solutions.

The article entitled "CMOS transceivers for the 60-GHz band" by B. Razavi, published in the digest of technical papers of the IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, 11-13 June 2006, pages 201-204, gives an overview of millimeter- wave CMOS transceiver design. It is mentioned that the integration of antennas on low-resistivity substrates presents a difficult challenge. Among microstrip, loop, slot and dipole structures, the last one exhibits the lowest loss, about -6 dB. A dipole has been realized in metal 8. The dipole is 1 mm long and 18 μm wide.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a wireless communication module with an integrated antenna that allows low-cost applications, in particular in the millimeter wavelength range. The independent claims define various aspects of the invention. The dependent claims define additional features for implementing the invention to advantage.

The invention takes the following points into consideration. In the millimeter wavelength band, a substrate of a typical CMOS integrated circuit will absorb radio frequency energy to relatively large extent. Consequently, radio frequency energy that is radiated into the substrate can be considered as substantially lost. A dipole antenna that has been formed on a main surface of an integrated circuit has a radiation pattern that is comparable with an ordinary formed dipole antenna. The dipole antenna will radiate an appreciable amount of power in directions that are substantially parallel to the main surface and thus radiate an appreciable amount of power into the substrate. Consequently, although the dipole antenna typically provides a better efficiency than other types of antennas in integrated circuit

implementations, the dipole antenna still suffers from a relatively poor efficiency. A relatively high level of radio frequency power needs to be generated on the integrated circuit in order to establish a wireless transmission over a given distance. This may require relatively expensive integrated circuit manufacturing techniques, or relatively expensive radio frequency circuits, or both.

In accordance with the invention, a wireless communication module comprises an integrated circuit that has a main surface on which an antenna has been formed. The antenna is arranged to have a radiation pattern that exhibits, in substantially any given plane that is perpendicular to the main surface, a lower gain in directions substantially parallel to the main surface than in other directions.

Accordingly, a relatively small amount power is radiated into the substrate. The antenna has a relatively high efficiency when formed on an integrated circuit. This allows a wireless transmission in the millimeter wavelength range over a given distance with relatively low radio frequency power. This may obviate a need for relatively expensive integrated circuit manufacturing techniques, or a need for expensive radio frequency circuits, or both. A cost reduction associated therewith will generally outweigh any additional costs that may be required to achieve the radiation pattern in accordance with the invention. For those reasons, the invention allows applications of wireless transmissions in the millimeter wavelength range at relatively low cost. An implementation of the invention advantageously comprises one or more of following additional features, which are described in separate paragraphs that correspond with individual dependent claims. Each of these additional features contributes to achieving low-cost applications that provide a satisfactory performance.

The antenna preferably comprises two dipole-like elements having respective dipole axes that are substantially parallel. The two dipole-like elements are aligned along an axis perpendicular to the respective dipole axes.

One dipole-like element is preferably larger than the other dipole-like element.

The two dipole-like elements are preferably formed by two tracks. A left track comprises two branches, one of which forms a left arm of one dipole-like element, the other branch forming a left arm of the other dipole-like element. A right track comprises two branches, one of which forms a right arm of one dipole-like element, the other branch forming a right arm of the other dipole-like element.

The left arm of one dipole-like element is preferably in the form of a coplanar winding. The same applies to the right arm of this dipole-like element.

The left arm of the other dipole-like element is preferably also in the form of a coplanar winding. The same applies to the right arm of this same dipole-like element. A feeding network preferably comprises a portion of the left track and a corresponding portion of the right track. A ground plane surrounds the respective portions of the left track and the right track that form part of the feeding network.

The feeding network preferably comprises short circuits between opposite sections of the ground plane that surrounds the left track and the right track. The short circuits are located relatively close to a bend in the left track and a bend in the right track.

A detailed description, with reference to drawings, illustrates the invention summarized hereinbefore as well as the additional features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that illustrates a data-handling apparatus, which is provided with a wireless communication module that includes an integrated circuit. FIG. 2 is a pictorial diagram that illustrates an antenna that forms part of the integrated circuit of the wireless communication module.

FIG. 3 is a pictorial diagram that illustrates floating metal islands, which are present between the antenna and a substrate of the integrated circuit.

FIG. 4 is a pictorial diagram that illustrates a cross-section of the integrated circuit that passes through the antenna.

FIG. 5 is a block diagram that illustrates a transmitter, which can apply a radio frequency signal to the antenna.

DETAILED DESCRIPTION FIG. 1 illustrates a personal computer PC that comprises a wireless communication module WCMl. The wireless communication module WCMl allows the personal computer PC to communicate data to a peripheral device PHD in a wireless fashion. Conversely, the wireless communication module WCMl may also allow the personal computer PC to receive data from the peripheral device PHD in a wireless fashion. The peripheral device PHD is also provided with a wireless communication module WCM2, which may be similar to the wireless communication module WCMl in the personal computer PC. A wireless communication between the personal computer PC and the peripheral device PHD may take place in a millimeter frequency band, for example, on a frequency of 60 GHz.

The wireless communication module WCMl of the personal computer PC comprises an integrated circuit IC that is mounted on a board. That is, the wireless communication module WCMl is in the form of a so-called die-on-board assembly. Bonding wires may electrically couple the integrated circuit IC to the board, which may comprise other electronic components. The board may comprise a metal plane, which at least partially covers a substrate of the integrated circuit IC. The metal plane is typically coupled to signal ground.

The integrated circuit IC comprises an antenna ANT, which has been formed on a main surface of the integrated circuit IC. That is, the antenna ANT is an integrated antenna in the sense that the antenna ANT has been formed while manufacturing the integrated circuit IC. The integrated circuit IC may comprise other functional entities, such as, for example a transmitter for applying a radiofrequency signal to the antenna ANT, or a receiver for processing a radiofrequency signal that the antenna ANT picks up. The integrated circuit IC preferably comprises all relevant high-frequency circuits, so that there is no need for any high-frequency coupling path between the integrated circuit IC and the board. The integrated circuit IC is preferably manufactured in high-frequency CMOS technology.

FIG. 2 illustrates the antenna ANT, which has been formed on the integrated circuit IC. A feeding network FN couples the antenna ANT to a transmitter circuit TX. The feeding network FN receives a differential antenna signal DAS, which carries data DA that the transmitter circuit TX receives. The differential antenna signal DAS has a frequency that may be controlled by means of a frequency control signal FC applied to the transmitter circuit TX.

The antenna ANT comprises two elements: a main compacted differential dipole MD and an auxiliary compacted differential dipole AD. These two dipole-like elements have respective dipole axes that are substantially parallel. The main compacted differential dipole MD and the auxiliary compacted differential dipole AD are aligned along an axis perpendicular to the respective dipole axes. The auxiliary compacted differential dipole AD is physically located between the feeding network FN and the main compacted differential dipole MD.

The main compacted differential dipole MD and the auxiliary compacted differential dipole AD are both formed in a single metal layer. This single metal layer is preferably a top metal layer of the integrated circuit IC. This top metal layer may be, for example, 600 nm thick. The antenna ANT is 860 micrometers (μm) wide and 410 μm long.

The auxiliary compacted differential dipole AD prevents the antenna ANT from radiating power into the substrate of the integrated circuit IC. Thanks to the auxiliary compacted differential dipole AD, the antenna ANT has a radiation pattern that has minima in directions substantially parallel to the substrate. The radiation pattern has maxima in directions perpendicular to the substrate. That is, the radiation pattern exhibits, in substantially any given plane that is perpendicular to the main surface of the integrated circuit IC, a lower gain in directions substantially parallel to the main surface than in other directions. The auxiliary compacted differential dipole AD forces the antenna ANT, as it were, to radiate power in directions other than those which are substantially parallel to the substrate of the integrated circuit IC.

The feeding network FN comprises two tracks Tl, T2 surrounded by a ground plane GP, which is provided with several metal underpasses MUl, MU2, MU3. The two tracks Tl, T2 comprise a left track Tl and a right track T2, which are each 42 μm wide. The left track Tl extends from the transmitter circuit TX to a left arm of the main compacted differential dipole MD and a left arm of the auxiliary compacted differential dipole AD. The right track T2 extends from the transmitter circuit TX to a right arm of the main compacted differential dipole MD and a right arm of the auxiliary compacted differential dipole AD.

The ground plane GP has been formed in the same metal layer as that in which the main and auxiliary compacted differential dipoles MD, AD are formed. The metal underpasses MUl, MU2, MU3 are formed in another metal layer, which lies beneath the aforementioned metal layer in a direction towards the substrate of the integrated circuit IC. The metal underpasses MUl, MU2, MU3 are located relatively close to bends, which are present in the two tracks Tl, T2. A metal under pass provides a short circuit between different sections of the ground plane GP just before a bend and just after a bend, as illustrated in FIG. 2.

The feeding network FN illustrated in FIG. 2 introduces little loss and has relatively little influence on the radiation pattern of the antenna ANT. The feeding network FN behaves as an almost ideal impedance converter, which matches an output impedance of the transmitter circuit TX to an input impedance of the antenna ANT. The metal underpasses MUl, MU2, MU3 contribute to achieving a low loss.

The left arm of the main compacted differential dipole MD constitutes a branch of the left track Tl, which passes through the feeding network FN. The left arm of the auxiliary compacted differential dipole AD constitutes another branch of the left track Tl. Similarly, the right arm of the main compacted differential dipole MD constitutes a branch of

the right track T2, which passes through the feeding network FN. The right arm of the auxiliary compacted differential dipole AD constitutes another branch of the right track T2. The left arm and the right arm of the main compacted differential dipole MD are symmetrical. The same applies to the left arm and the right arm of the auxiliary compacted differential dipole AD.

More specifically, the left arm of the main compacted differential dipole MD is in the form of a small coplanar winding with one and a half turns. The same applies to the right arm of the main compacted differential dipole MD for reasons of symmetry. The left arm of the auxiliary compacted differential dipole AD is also in the form of a small coplanar winding with one and a half turns. The same applies to the right arm of the auxiliary compacted differential dipole AD for reasons of symmetry. The respective coplanar windings that form the respective arms of the auxiliary compacted differential dipole AD are somewhat larger than the respective coplanar windings that form the respective arms of the main compacted differential dipole MD. There is a particular spacing between two parallel track portions in each of the aforementioned coplanar windings. This particular spacing is preferably adjusted to a frequency of operation, which is, for example, 60 GHz. That is, the spacing between two parallel track portions can be regarded as a parameter, which should be correctly tuned. The substrate of the integrated circuit IC is preferably relatively thin. The antenna ANT has a gain that increases with decreasing thickness of the substrate. The thinner the substrate is, the lesser the portion is of radiated power that is lost in the substrate. For example, a satisfactory gain can be achieved when the substrate is 250 μm thick. This thickness can be obtained by graining a wafer that was originally 550 μm thick. This graining can be post-processing step, which may be carried out before the wafer is diced so as to obtain individual integrated circuit ICs. Reducing the thickness of the substrate from 550 μm to 250 μm provides an increase of antenna gain by approximately 7.5 decibel (dB).

The antenna ANT illustrated in FIG. 2 has been a subject of computer simulations. The substrate was of the CMOS type and 250 μm thick. A perfect conductor was assumed to be present on a backside of the integrated circuit IC, which is the side that is opposite to the side on which the antenna ANT has been formed. This perfect conductor corresponds with the ground plane on the board mentioned hereinbefore in connection with FIG. 1. The computer simulations provided the following results.

The gain of the antenna ANT in so-called odd-mode excitation at 60 GHz is -6.5 dB. The antenna ANT has a -10 dB bandwidth that ranges from 58 GHz to 70 GHz. The

antenna ANT has an efficiency of 4.6%, which is relatively low compared with conventional antennas that do not form part of an integrated circuit IC. This is because a substantial amount of radiated power is absorbed in the substrate, which is of the CMOS type. However, the efficiency would have been lower if a conventional dipole had been used as an integrated antenna ANT. It should be noted that the relatively low efficiency is not necessarily a problem for short-range communications or other applications that do not require high radiated power levels.

The computer simulations have also confirmed that the gain of the antenna ANT would drop from -6.5 dB to -14 dB if the substrate was 550 μm thick. This corresponds with a doubling of losses due to the substrate. Moreover, the antenna ANT would have an optimum operating frequency of 68 GHz instead of 60 GHz. Consequently, in case the substrate was 550 μm thick, the antenna ANT would have to be larger in order to bring the optimum operating frequency at 60 GHz.

FIG. 3 illustrates a set of floating metal islands FMI that substantially coincide with the two tracks Tl, T2 in an area where the antenna ANT has been formed. The set of floating metal islands FMI constitute tiles that are formed in metal layers, which are located beneath the top metal layer in which the antenna ANT has been formed. The floating metal islands FMI are present in order to comply with design rules that applied to the integrated circuit IC. Modern CMOS processes typically require such a tiling in order to guarantee appropriate metal densities.

FIG. 4 illustrates a cross-section of the integrated circuit IC along a line I-II indicated in FIG. 3. This cross-section traverses the left track Tl that has been formed in a sixth metal layer ME6, which is the top layer of the integrated circuit IC. The floating metal islands FMI are formed in each of the other metal layers, the first to fifth metal layers MEl- ME5, which are located beneath the sixth metal layer ME6.

It has been found that the floating metal islands FMI have little influence on the optimum operating frequency, the gain, and the radiation pattern of the antenna ANT. A substantial magnitude difference was found between cross and co-polarization: co- polarization dominates over cross polarization. FIG. 5 illustrates an implementation of the transmitter circuit TX. The transmitter circuit TX comprises a frequency synthesizer FSY that is provided with a crystal resonator XT, a controllable oscillator VCO, and two mixers MIXl, MIX2. The transmitter circuit TX further comprises a baseband and modulation processor BBMP, two controllable amplifiers PAMl, PAM2, and two summing circuits SUMl, SUM2.

The transmitter circuit TX basically operates as follows. The frequency synthesizer FSY, the controllable oscillator VCO, and the two mixers MIXl, MIX2 constitute a circuit arrangement that generates two radiofrequency carrier signals IC, QC that have a phase quadrature relationship: an in-phase carrier signal IC and a quadrature carrier signal QC. These carrier signals have a frequency that is determined by the frequency control signal FC, which the transmitter circuit TX receives.

In more detail, the controllable oscillator VCO provides a set of four oscillator signals that are phase shifted with respect to each other: a 0 phase oscillator signal, a π/4 phase oscillator signal, a π/2 phase oscillator signal, and a 3 π/4 phase oscillator signal. These four oscillator signals have a frequency that is half the frequency of the aforementioned carrier signals. Mixer MIXl multiplies the 0 phase oscillator signal with the π/2 phase oscillator signal so as to obtain the in-phase carrier signal IC. Mixer MIX2 multiplies the π/4 phase oscillator signal with the 3π/4 phase oscillator signal so as to obtain the quadrature carrier signal QC. The two mixers MIXl, MIX2 thus effectively behave as frequency doubling circuits. The controllable oscillator VCO applies an auxiliary oscillator signal OS to the frequency synthesizer FSY. In response, the frequency synthesizer FSY applies a tuning signal TS to the controllable oscillator VCO so that the frequency of the set of four oscillator signals is equal to a desired frequency of the radiofrequency carrier signals IC, QC divided by two. The frequency synthesizer FSY generates the tuning signal TS on the basis of the crystal resonator XT and the frequency control signal FC.

The baseband and modulation processor BBMP generates two amplitude modulation signals IM, QM on the basis of the data DA to be transmitted: an in-phase amplitude modulation signal IM and a quadrature amplitude modulation signal QM. Power amplifier PAMl receives the in-phase amplitude modulation signal IM as a gain control signal. Power amplifier PAM2 receives the quadrature amplitude modulation signal QM as a gain control signal. Accordingly, power amplifier PAMl and power amplifier PAM2 provide an amplitude modulated in-phase carrier signal ICM and an amplitude modulated quadrature carrier signal QCM, respectively. The two amplitude modulation signals IM, QM are so that when the two aforementioned amplitude modulated carrier signals ICM, QCM are summed together, or subtracted from each other, a phase modulated signal is obtained that carries the data DA to be transmitted.

Summing circuit SUMl subtracts the amplitude modulated quadrature carrier signal QCM from the amplitude modulated in-phase carrier signal ICM. Accordingly, summing SUMl circuit provides a first antenna signal ASl, which has a phase modulation

that represents the data DA to be transmitted. Summing circuit SUM2 adds the aforementioned modulated carrier signals ICM, QCM together. Accordingly, summing circuit SUM2 provides a second antenna signal AS2, which also has a phase modulation that represents the data DA to be transmitted. The first antenna signal may correspond with the differential antenna signal DAS illustrated in FIG. 2. The second radio frequency antenna signal AS2 may be applied to another antenna that is similar to the antenna ANT illustrated in FIG. 2. The use of two or more antennas allows beam forming and beam steering. Beam forming is a technique that employs several antennas to concentrate radiated power in a particular direction. Beam steering implies beam forming and adds an aspect of controlling the particular direction in which radiated power is concentrated.

The antenna ANT illustrated in FIG. 2 may also be coupled to a receiver circuit. That is, an integrated antenna may be shared by a receiver circuit and a transmitter circuit if it is ensured that, at any given time, only one of these circuits operates. This can be achieved by means of time division multiple access (TDMA). Such an operation is preferred because it requires a smaller integrated surface area to form antennas, compared with a solution wherein one or more antennas are dedicated to reception whereas one or more other antennas are dedicated to transmission.

CONCLUDING REMARKS The detailed description hereinbefore with reference to the drawings is merely an illustration of the invention and the additional features, which are defined in the claims. The invention can be implemented in numerous different manners. In order to illustrate this, some alternatives are briefly indicated.

The invention may be applied to advantage in any type of product or method that involves a wireless transmission. A wireless communication between two data-handling apparatuses, as illustrated in FIG. 1, is merely an example. The invention may equally be applied to advantage in, for example, imaging applications for medical, security, or industrial purposes. Such an application requires an array of integrated circuits provided with an antenna and a receiver circuit or a transmitter circuit, or both. The array of integrated circuits surrounds an object of interest. One of the integrated circuits is in a transmitting mode, whereas the other integrated circuits are in a receiving mode. The object of interest will cause a back scattering of transmitted energy, which will be received by the integrated circuits that are in the receiving mode. An image of the object of interest can be formed on the basis of this received back scattering energy. Appropriate processing is required. The image will have

a resolution that depends on parameters such as frequency and bandwidth. These parameters also determine a depth of view, that is, how deep one can view into the object of interest. Such an imaging applications, which is based on an array of integrated circuits provided with antennas, can be implemented at relatively low cost. Moreover, integrated antennas are relatively well protected against environmental factors, such as, for example, humidity.

There are numerous ways of implementing an antenna in accordance with the invention. FIG. 2 illustrates an example in which the antenna ANT comprises two dipole-like elements: a main compacted differential dipole MD and an auxiliary compacted differential dipole AD. It is possible to add further compacted differential dipoles. Antenna elements need not necessarily be in the form of compacted differential dipoles as illustrated in FIG. 2. For example, an antenna element may be in the form of a conventional dipole, although this requires a larger integrated surface area.

There are numerous ways of implementing functions by means of items of hardware or software, or both. In this respect, the drawings are very diagrammatic, each representing only one possible embodiment of the invention. Thus, although a drawing shows different functions as different blocks, this by no means excludes that a single item of hardware or software carries out several functions. Nor does it exclude that an assembly of items of hardware or software or both carry out a function.

The remarks made herein before demonstrate that the detailed description with reference to the drawings, illustrate rather than limit the invention. There are numerous alternatives, which fall within the scope of the appended claims. Any reference sign in a claim should not be construed as limiting the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in a claim. The word "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.