GB2524761A - Wireless transceiver using an electromagnetic lens antenna - Google Patents

Abstract

A transmission signal and receiver signal antenna arrangement comprises an electromagnetic lens 302 having a variation in permittivity along a predetermined plane for guiding signals along the said plane. A plurality of radiating elements and a plurality of detecting elements are arranged along a line that lies within the said plane. The said elements may be narrow beam, closely packed waveguides or striplines, with no gap between them. The lens 302 may be a Luneburg lens. Also disclosed is a method of operating a communication signal transceiver which comprises determining a first element of the transceiver that radiates or detects electromagnetic signals when the transceiver is in communication, in a first direction, with a remote device. Then selecting a second element of the transceiver, that is adjacent to the determined first element, and activating the second element for communication with the device in the reverse communication direction to that of the first element. The antenna arrangement may be compact, easy to use and capable of operating in full or half duplex communications.

Description

Wireless transceiver using an electromagnetic lens antenna The invention belongs to the field of antennas and radiating devices, and more specifically to millimeter wave devices aiming at providing indoor and/or outdoor wireless communications.

Recent multimedia applications, such as uncompressed video streaming, require high data rate transmission of the order of several Giga bits per second (Gbps). For instance, a full HD video stream requires a throughput of about 3Gbps (1 920x1 080 pixels in a frame, 24 bits/pixel, 60 frames per second). Transferring uncompressed video has the benefit of obtaining a high quality video available at low latency since no compression/decompression is performed. This makes it possible for example to implement systems involving high interactivity such as simulation tools.

To increase the transmission rate, higher frequencies may be used, for instance the 57-66 GHz millimeter-wave unlicensed frequency band, referred to as 60 GHz millimeter wave technology. However, the transmission power in the 60 GHz band is limited to 40 dBm by the FCC (Federal Communications Commission). Furthermore, radio waves in this frequency band are prone to absorption and to attenuation by the oxygen molecules of the air, which makes them unsuitable for long range transmissions.

One solution to increase the transmission range is to use beam forming techniques by means of smart antennas or lens based antennas (e.g. Luneburg). Lens based antennas rely on the use of an electromagnetic lens, of spherical or cylindrical shape, having a gradient of decreasing refractive index for guiding the waves within the lens. The lens is generally provided either with detecting elements or with radiating elements depending on whether the antenna is to be used for transmission or reception.

However it is highly desirable to have bi-directional communications to support control protocols between a source device and a destination device. Such protocols can be related to the antenna discovery operation to find best antenna settings (direction) for the transmitter and the receiver. They can also be related to an automatic repeat request (ARO) mechanism where the receiver requests the emitter to retransmit some corrupted received data.

Finally, integration of wireless transceivers in a multimedia product should be done at the lowest extra cost, and with the smallest impact on the product design (weight, aesthetic...).

The three constraints listed above (long range, bi-directional, bulk) are difficult to combine in a single design, and it appears that radio designs available today do not completely satisfy these requirements.

The present invention has been devised to address at least the foregoing concern.

SUMMARY OF THE INVENTION

To this end, the present invention provides according to a first aspect a transceiver comprising: an electromagnetic lens having a variation in permittivity along a predetermined plane for guiding electromagnetic signals along said predetermined plane; a plurality of radiating elements configured to radiate electromagnetic signals into the electromagnetic lens, the radiated electromagnetic signals being then guided by the electromagnetic lens; and a plurality of detecting elements configured to detect electromagnetic signals radiated out of the electromagnetic lens, the detected electromagnetic signals being guided by the electromagnetic lens prior their detecting therefrom; wherein the radiating elements are positioned in alternation relatively to the detecting elements along the predetermined plane.

As a result of the alternation between the radiating elements and the detecting elements, a single lens can be used and the transceiver can operate in half duplex mode and in full duplex mode while keeping the transceiver's bulk small. A small transceiver with integrated antenna can thus be achieved.

Preferably, adjacent radiating/detecting elements are kept close to each other with no gap between them According to one implementation, the plurality of radiating elements and the plurality of detecting elements are implemented using waveguides.

According to one implementation, the electromagnetic lens is a Luneburg lens with a refraction index of E(r) = 2 -r2, where r is the normalized radius.

The present invention provides according to a second aspect a method of configuring a transceiver for a communication with a remote device, the transceiver comprising an electromagnetic lens having a variation in permittivity along a predetermined plane for guiding electromagnetic signals along said predetermined plane, a plurality of radiating elements configured to radiate electromagnetic signals into the electromagnetic lens and a plurality of detecting elements configured to detect electromagnetic signals radiated out of the electromagnetic lens and positioned in alternation relatively to the radiating elements along the predetermined plane. The method comprising: determining a first element of the transceiver that radiates or detects electromagnetic signals when the transceiver is in communication in a first direction with the device; selecting a second element of the transceiver that is adjacent to the determined element; and activating the second element for communicating with the device in the reverse direction.

As a result, in the context of a narrow beam discovely process for example, when an orientation is found for establishing a path in one direction, say from a server device to a client device, the method is advantageously used to quickly configure the orientations for the path in the reverse direction, i.e. from the client to the server.

In fact, if for example a transmission beam has to be oriented in substantially the same direction than a given reception beam (e.g. because the transmitted signal is to be addressed to same device from which a signal has been received using the given reception beam), it suffices to enable one (or more) radiating element(s) that is(are) adjacent to the detecting element from which the received signal has been detected. As a result, a transmission beam is generated in substantially the same direction than the direction of the received beam without having to calculate reception and transmission angles. Conversely, if a reception beam has to be oriented in the same direction than a given transmission beam, it suffices to enable one (or more) detecting element(s) that is(are) adjacent to the radiating element from which the transmitted signal has been emitted.

Advantageously, the selecting of the second element is based on the signal strength radiated or detected at the elements surrounding the first element.

More particularly, when the first element is a detecting element and the second element is a radiating element, the selecting of the second radiating element comprises: selecting a third detecting element associated with the highest signal strength detected among the detecting elements surrounding the first detecting; and selecting as second radiating element the element that is adjacent to both the first detecting element and the third detecting element.

Thus, the orientation of the beam in the reverse direction is made more accurate.

In one implementation, the communication in the first direction and the communication in the reverse direction are performed in half-duplex mode using a same frequency band.

In another implementation, the communication in the first direction and the communication in the reverse direction are performed in full-duplex mode using respectively distinct frequency bands.

The present invention also extends to programs which, when run on a computer or processor, cause the computer or processor to carry out the method described above or which, when loaded into a programmable device, cause that device to become the device described above. The program may be provided by itself, or carried by a carrier medium. The carrier medium may be a storage or recording medium, or it may be a transmission medium such as a signal. A program embodying the present invention may be transitory or non-transitory.

The particular features and advantages of the transmitting and receiving devices and the program being similar to those of the methods for transmitting and receiving data blocks, they are not repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts for illustrative purposes a multi-projection system in which an embodiment of the invention can be implemented.

Figure 2 shows a functional block diagram of a wireless transceiver.

Figure 3 represents an implementation of the physical layer module showing in particular the transmission components.

Figure 4 represents an implementation of the physical layer module showing in particular the reception components.

Figure 5 represents a superposition of figure 3 and figure 4 illustrating alternation of waveguides for transmission beams and waveguides for reception beams.

Figures 6a and 6b represent a side view of an antenna according to different implementation variants.

Figures 7a and 7b depict flowcharts of the antenna discovery process according to a first embodiment of the invention to be executed by two wireless transceivers.

Figures 8a and 8b depict flowcharts of the antenna discovery process according to a second embodiment of the invention to be executed by two wireless transceivers.

Figure 9 is a flowchart of the antenna discovery process according to a third embodiment of the invention to be executed by a wireless transceiver.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 depicts for illustrative purposes a wireless multi-projection system operating in the 60GHz frequency band in which an embodiment of the invention can be implemented. The multi-projection system is composed of one video projector 104 installed on a metallic structure ill hooked to a room ceiling 110. The video projector is wirelessly connected to a video source device 102. A 60GHz wireless transceiver 101 is attached to the video source device 102 for running the wireless connection. The video projector is equipped with an optical zoom lens 105 adjusted to a given focal length, and with a 60GHz wireless transceiver 103 that may be similar to wireless transceiver 101.

The antenna system of transceiver 103 is configured to have a radiation pattern (for emission and/or reception) covering an area 107 between the ceiling 110 and the ground 112. The antenna system of transceiver 101 is configured to have a radiation pattern (for emission and/or reception) covering an area 108 between the ceiling 110 and the ground 112.

It is assumed that the antenna technology used in this embodiment uses beam forming relying on an electromagnetic lens of cylindrical shape as it will be detailed hereinafter. In alternate embodiments, the lens may have other shapes such as a sphere or half a sphere.

The video source device 102 may be a digital video camera, a hard-disk drive or a solid-state drive, a digital video recorder. a personal computer, a set-top box, a video game console or similar.

Figure 2 shows a functional block diagram of a wireless transceiver, such as the wireless transceiver 101 or 103 of figure 1. The wireless transceiver comprises: * a main control unit 201, and * a physical layer unit (denoted PHY) 211.

The main control unit 201 may comprise the following functional blocks: * a Random Access Memory (denoted RAM) 233, * a Read-Only Memory (denoted ROM) 232, * a micro-controller or Central Processing Unit (denoted CPU) 231, * a user interface controller 234, * a medium access controller (denoted MAC) 238, * a video processing controller 235, * a video input interface controller 236, * a video output interface controller 239, and * a video Random Access Memory (denoted video RAM) 237.

CPU 231, MAC 238, video processing controller 235, user interface controller 234 exchange control information via a communication bus 244, on which is also connected RAM 233 and ROM 232. CPU 231 controls the overall operation of the wireless transceiver as it is capable of executing, from the memory RAM 233, instructions pertaining to a computer program, once these instructions have been loaded from the memory ROM 232, or from any other internal or external unit.

Thanks to the user interface controller 234, it is possible for an installer to configure the wireless transceiver. This interface can be a wired interface (like Ethernet, Universal Serial Bus USB) or a wireless interface (infrared, Wi-Fi (RTM)). The installer's settings are stored in RAM memory 233.

The video processing controller 235 processes, when necessary, video data either received from one of the Video input 236, the Video RAM 237 and the MAC 238, or prior its transmission to one of the Video output 239, the Video RAM 237 and the MAC 238. For example, the video processing controller 235 may apply error concealment to the corrupted video data received from the network, via the MAC 238.

MAC 238 is in charge of controlling the emission and reception of MAC frames conveying control data and payload data (e.g. video data). For physical transmission and reception, the MAC 238 relies on the physical layer unit 211. Preferably, the physical layer unit operates in the 60GHz band. Typically, useful throughput between MAC 238 and the physical layer unit 211 is in the order of 3.5Gbps.

The physical layer unit 211 embeds a modem 212, a radio module 213 and an antenna 214. In one embodiment of the invention, the antenna 214 is a cylindrical lens antenna. The radio module 213 is responsible for processing a signal output by the modem 212 before it is sent out by means of the antenna 214. Conversely, the radio module 213 is also responsible for processing a signal received by the antenna 214 before it is provided to the modem 212. The radio module 213 is mainly in charge of up- converting and down-converting signals frequency. For transmission, it provides up-conversion from the low frequency of the modem to the high frequency of radio signals (carrier). For reception, it provides the reverse operation, i.e. down-conversion from high to low frequency. The operational frequency of the carrier is for example in the 60GHz frequency band.

The modem 212 is responsible for modulating and demodulating the digital data exchanged with the radio module 213. For instance, the modulation and demodulation scheme applied is of Orthogonal Frequency-Division Multiplexing (OFDM) type. The elements of physical layer 211 are driven by the CPU 231 through the MAC 238.

MAC 238 acts as a synchronization control unit, which controls scheduling of transmissions via the network. It means that MAC 238 schedules the beginning and the end of an emission of radio frames over the medium, as well as the beginning and the end of a reception of frames from the medium.

If we consider the reception side, the modem of physical layer unit 211 collects the radio frames received from the radio module through the reception antenna 214, and transmits the received radio frames to the MAC 238. The MAC 238 is therefore able to detect if a radio frame is missing. This detection is made when the MAC 238 is expecting a radio frame payload during a scheduled reception time slot and no data is delivered by the physical layer unit. This situation may occur when the modem has failed to recognize the radio frame preamble, i.e. the synchronization was unsuccessful because the signal-to-noise ratio (SNR) or received signal strength indication (RSSI) was too low (the signal has been indiscernible from noise). Also, MAC 238 is able to detect transmission errors within a radio frame. As a radio frame payload can be divided into several packets, CRC (Cyclic Redundancy Check) data computed by MAC 238 can be appended at the end of each packet. For a given packet received in a destination node, if the CRC computation result is different from what is received with the packet, the MAC 238 may decide to drop this packet as it is very likely to contain errors. Therefore, MAC 238 can indicate to video processing controller 235 if some packets are missing or containing errors. Any appropriate error concealment or retransmission mechanism can be applied afterwards by the video processing controller 235 to recover lost information.

Figure 3 depicts an implementation of the physical layer module 211 of figure 2, showing, in particular, transmission components.

The physical layer 211 may include a main printed circuit board (PCB) 301 dedicated to digital baseband processing on which is soldered a second printed circuit board (PCB) 310 dedicated to the high frequency transmission part of the design.

The unit 303 represents the digital baseband chip integrating the modem 212. In the depicted implementation, the chip 303 is soldered on one (upper) side of PCB 301.

On PCB 310 is installed a radio transmitter chip 304 and transmission lines for dispatching the radio frequency output signal 307 of chip 304 towards a plurality of radiating elements 351 -358 for illuminating an electromagnetic lens antenna 302. The radiating elements are typically electromagnetic waveguides. Alternatively, the radiating elements may be implemented using striplines.

The lens 302 is inhomogeneous in terms of permittivity with focusing and beam forming capabilities. The refraction index n(r) inside the lens follows a radial distribution.

The most known example of this type of lens is the Luneburg lens. For a Luneburg lens, the refraction index law is governed by the following formula: n2(r) = E(r) = 2 -r2, where r is the normalized radial position.

In a conventional Luneburg lens, the dielectric constant varies from 2 in the center of the lens and decreases to 1 on its surface. These example values are used in embodiments of the invention, but other values may be considered as well.

Also, in embodiments of the invention, a Luneburg lens of cylindrical shape is considered. The cylindrical lens is formed for example by a superposition of homogeneous layers of materials substantially concentric around the symmetry axis of said electromagnetic lens and (partially) encapsulated by an upper and a lower parts of an enclosure to confine the electromagnetic waves in the axial direction. Such an arrangement results into a narrow beam in azimuth (radial) plane and a relatively large beam in the elevation (axial) plane.

In a variant, the cylindrical electromagnetic lens is sandwiched between two metal shielding members.

Thanks to these metal shielding members, an electromagnetic signal that propagates in the lens may be guided in a direction that is substantially parallel to the variation in permittivity (i.e. parallel to the permittivity gradient) of the electromagnetic lens. This guidance contributes to obtain a large elevation pattern of the main beam while ensuring a narrow beam in azimuth. It also contribute to orientate said narrow beam within a very large sector in azimuth.

The antenna gain value depends on the radius of the lens 302. For example, l5dBi can be obtained with a radius of about 30mm.

The lens 302 is illuminated in the illustrated example by 8 radio wave sources 351 -358. These sources are antenna (radiating) elements placed over the circular surface of the cylindrical lens. On this particular embodiment, these antenna elements are waveguides supplied by power amplifiers (PA) referenced from 321 to 328.

For transmission, an On/Off command on the power amplifier (not represented) enables to activate/disable each single beam. The command signals come from the CPU 231 through the MAC 238. Activation of amplifier 321 for example will produce the beam 311 represented in the figure. In the same way, the beam 315 is produced through the activation of amplifier 325 and the beam 318 is produced through the activation of amplifier 328. If only one waveguide is supplied by a signal, the antenna would form thus a narrow beam through the lens, characterized by a width of 200 in the azimuth plan.

However, several waveguides can be supplied simultaneously by signals after the activation of their corresponding PAs to form a larger beam by aggregation. If all waveguides are supplied, this results into a wide beam. Two adjacent beams radiate in two main directions separated by 200 corresponding to the difference of orientation of two adjacent waveguides. This makes it possible to cover in total a range of 1600 for transmission.

Figure 4 depicts an implementation of the physical layer module 211 of figure 2 showing, in particular, reception components. Same components with figure 3 hold same reference numbers.

The physical layer 211 may include, in addition to the main PCB 301 and the second PCB 310 dedicated to the high frequency transmitting part of the design, a third printed circuit board (P08) 410 dedicated to the high frequency receiving part of the design. This third PCB 410 is for example soldered to PCB 301 in the side opposite to P08 310.

On PCB 410 is installed a radio receiver chip 305 and reception lines for collecting signals from a plurality of detecting elements 451 -458 for providing a radio frequency input signal 407 to radio receiver chip 305. The signals are detected at the surface of the electromagnetic lens 302.

The detecting elements 451 -458 are typically electromagnetic waveguides.

Alternatively, the detecting elements may be implemented using striplines. The detecting elements are associated with a low noise amplifiers (LNA) referenced from 421 to 428.

For reception, an On/Off command on a low noise amplifier (not represented) enables to activate/disable each single beam. The command signals come from the CPU 231 through the MAC 238. Activation of amplifier 421 for example will enable reception from the beam 411. In the same way, the beam 415 is selected through the activation of amplifier 425 and the beam 418 is selected through the activation of amplifier 428. Each beam is characterized by a width of 20° in the azimuth plane. Two adjacent beams radiate in two main directions separated by 20° corresponding the difference of orientation of two adjacent waveguides. This makes it possible to cover a range of 160° in total for reception.

Figure 5 is a superposition of figure 3 and figure 4 aimed to show circuits of both P08 310 and 410 (same references kept from figures 3 and 4). Circuits of PCB 410 are represented in dotted lines. The superposition shows the alternation of radiating elements and detecting elements. It can be seen that a same lens 302 can advantageously be shared for both transmission and reception.

The angle between one radiating element (waveguide for transmission) and each adjacent detecting element (waveguide for reception) represents 10° in this embodiment.

As a result of the alternation between the radiating elements and the detecting elements, a single lens can be used and the transceiver can operate in half duplex mode and in full duplex mode while keeping the transceiver's bulk small. A small transceiver with integrated antenna can thus be achieved.

In a preferred implementation, adjacent radiating/detecting elements are kept close to each other, with small or even no gap between them. This advantageously reduces the granularity of the angles that can be chosen for emission or reception.

Furthermore this arrangement makes it possible to ease the setting of emission/reception directions of the beam in case of symmetrical communication paths. In fact, if for example a transmission beam has to be oriented in substantially the same direction than a given reception beam (e.g. because the transmitted signal is to be addressed to same device from which a signal has been received using the given reception beam), it suffices to enable one (or more) radiating element(s) that is(are) adjacent to the detecting element from which the received signal has been detected. As a result, a transmission beam is generated in substantially the same direction than the direction of the received beam without having to calculate reception and transmission angles. Conversely, if a reception beam has to be oriented in the same direction than a given transmission beam, it suffices to enable one (or more) detecting element(s) that is(are) adjacent to the radiating element from which the transmitted signal has been emitted.

The setting of the emission/reception directions as discussed above is efficient because it is hardware based, i.e. there is no need to calculate angles as intermediate means to associate one (or more) radiating beam(s) with one (or more) detecting beam(s).

In half duplex mode, transmission and reception are not simultaneous but the same radio frequency channel can be used for both operations. In full duplex mode, emission and reception are simultaneous and interference are avoided by selecting a first radio frequency channel for emission and a second radio frequency channel for reception.

Other arrangements may be considered in other embodiments, by varying for example the number of radiating and/or detecting elements and the gap (angle) between two adjacent radiating/detecting elements. This arrangements may be chosen to fit specific wireless system requirements.

Figure 6a represents two cross-section views A and B of physical layer module 211.

Cross-section view A shows a radiating element 355 and the corresponding PA 325 soldered to PCB 310. This cross-section view also shows the lens 302, and the output beam 315 represented with the resulting aperture in elevation (axial) plane in the order of 700 (linked to the thickness of the lens).

Cross-section view B shows a detecting element 455 and the corresponding [NA 425 soldered to PCB 410. This cross-section view also shows the lens 302, and the input beam 415 represented with the resulting aperture in elevation (axial) plane in the same order of 70° (linked to the thickness of the lens).

Figure 6b represents two cross-section views A and B of an alternate implementation of physical layer module 211. In this alternate implementation, all the components are soldered to one main PCB 381, one side of the PCB holding the components for transmission (PA 325, radiating element 355) and the other side of the PCB holding the components for reception ([NA 425, detecting element 455).

Figures 7a, 7b, 8a, Sb and 9 describe various embodiments of an antenna discovery process that takes advantage of the architecture of the radio modules and antennas as described in figures 3 to 5.

The discovery process is a process used to determine the best orientation for a couple of antennas, the antenna of the video source (referred to as server device) and the antenna of the video projector (referred to as client device), to establish a communication path using narrow beams at both devices. When the orientations are found for establishing a path in one direction, say from the server to the client, arrangements of the antennas according to embodiments of the invention are advantageously used to quickly configure the orientations for the path in the reverse direction, i.e. from the client to the server, as it will be detailed hereinafter.

According to the described embodiments, the antenna discovery process consists basically in the following phases: -an emitting phase during which a first device sends a reference signal (test pattern) in one or more directions; -a scanning phase during which a second device scans, while the first device is in emitting phase, different possible orientations and searches for the orientation giving the best or acceptable received signal strength indication (RSSD; and -a communication phase during which a communication can be established between the first and the second devices using the best or acceptable orientation found during the scanning phase.

It is assumed in all the following embodiments that the antenna of each device comprises M radiating elements (RE) and N detecting elements (DE).

Figures 7a and 7b depict flowcharts of the antenna discovery process according to a first embodiment.

Figure 7a is a flowchart of the algorithm executed by CPU 231 at the initialization of wireless transceiver 101 of video source device 102 (server). Figure 7b is a flowchart of the algorithm executed by CPU 231 at the initialization of wireless transceiver 103 of video projector 104 (client). These two flowcharts are executed in parallel and synchronized at their phases (represented by dotted arrows), i.e. the emitting phase of the server is synchronized with the scanning phase of the client, the emitting phase of the client is synchronized with the scanning phase of the server, and the communication phases of both devices are synchronized with each other. By synchronization it is meant that the phases have to start substantially at the same time.

The wireless transceiver 101 of video source device 102 (server) initiates the antenna discovery process by activating all beams associated with the radiating elements (from RE(1) to RE(M)), e.g. by transmitting a command activation signal to their corresponding power amplifiers (step 701). In fact, in this embodiment it is assumed that during the emitting phase of the server, a signal (could be a test pattern) is emitted in all possible directions (similar to broadcast) to accelerate the discovery process (step 702).

While the server is transmitting the signal during the emitting phase, the client enters a scanning phase during which the N possible beam directions are tested. This is performed by iteratively activating each detecting element DEU) (step 711) and determining the RSSIU) of the signal detected at that detecting element DE(j) (step 712).

The activation of the detecting element can be performed by sending a command to the corresponding low noise amplifier. The detecting element, say DE(n), for which, preferably, the maximum RSSI has been determined is then selected (step 713). The beam orientation corresponding to this selected detecting element n will be used in the communication phase for receiving signals from the server using narrow beams (step 717).

In order to configure the communication path from the client device to the server device, a radiating element, say RE(m), that is adjacent to DE(n) is selected without further scanning process (step 714). Indeed, the two elements being adjacent, the corresponding beams are considered to have substantially the same orientations (e.g. 10° degrees in the antenna implementation examples discussed above). Thus, the beam orientation corresponding to this selected radiating element m will be used in the communication phase for transmitting signals to the server using narrow beams (step 717).

This orientation (associated with RE(m)) will be also used to send a signal (test pattern) to the server to enable the server to configure its antenna parameters. Indeed, since the server transmits signals simultaneously over all the beams during the emitting phase, a further scanning phase needs to be performed in order to determine which couple of detecting element DE(n') and radiating element RE(m) should be used by the server to transmit signals to, or received signals from, the client using narrow beams.

Typically a narrow beam corresponds to the beam generated, or detected, respectively, by a single radiating element or a single detecting element. A narrow beam can be extended to a beam generated or detected by two or few more elements.

Thus the client device activates beam m associated with the radiating element RE(m) to prepare for the transmission of the signal to the server device (step 715). This is performed for example by transmitting a command activation signal to the corresponding power amplifier.

When the server enters the scanning phase, the client starts its emitting phase by transmitting a signal (could be test pattern) in the configured orientation (activated beam) using radiating element RE(m) (step 716).

During the scanning phase, the server tests the N possible beam directions. This is performed by iteratively activating each detecting element DEO) (step 703) and determining the RSSIO) of the signal detected at that detecting element DEC) (step 704).

The activation of the detecting element can be performed by sending a command to the corresponding low noise amplifier. The detecting element, say DE(n'), for which, preferably, the maximum RSSI has been determined is then selected (step 705). The beam orientation corresponding to this selected detecting element n' will be used in the communication phase for receiving signals from the client using narrow beams (step 708).

In order to configure the communication path from the server device to the client device, a radiating element, say RE(m"), that is adjacent to DE(n') is selected without further scanning process (step 706). Indeed, the two elements being adjacent, the corresponding beams are considered to have substantially the same orientations (e.g. 10° degrees in the antenna implementation examples discussed above). Thus, the server device activates beam m' associated with the radiating element RE(m) (step 707) and the beam orientation corresponding to this selected radiating element m' will be used in the communication phase for transmitting signals to the client using narrow beams (step 708).

Figures 8a and 8b depict flowcharts of the antenna discovery process according to a second embodiment.

Similarly to figures 7a and 7b, figures 8a and 8b depict flowcharts of the algorithms executed by CPU 231 at the initialization of, respectively, the wireless transceiver 101 of video source device 102 (server) and the wireless transceiver 103 of video projector 104 (client).

In this second embodiment however, scanning the different orientations at the client side is performed for each orientation of the beam at the server side. This is contrary to simultaneous transmissions of signals in all possible directions of the first embodiment. Although this takes more time at the beginning, it is advantageous in the sense that it is possible to identify during this phase the orientation of the communication path to be used to communicate with the client device using narrow beams, i.e. it allows the identification of RE(m').

The wireless transceiver 101 of video source device 102 (server) initiates the antenna discovery process by iteratively activating each radiating element RE(i) (step 801) and transmitting a signal (could be a test pattern) using the activated REO) (step 802). Here the transmission of the signal lasts a predetermined duration, i.e. a time-slot, that is sufficiently long to let the client scan all possible directions.

The wireless transceiver 103 of video projector 104 (client) initiates the antenna discovery process and the scanning phase by iteratively synchronizing with the start of each time-slot i of the server device. This synchronization can be performed by communication means, for example by adding a preamble at the start of each time-slot enabling the device to identify the beginning of the time-slot and its index i.

During each time-slot, the client scans the N possible beam directions by executing steps 811 and 812 in a similar way to steps 711 and 712 of figure 7b, except that they are repeated for each time-slot.

At the end, the client has to select a detecting element ii (DE(n)) for which, preferably, the maximum RSSI has been determined among the set of determined RSSI(i)(j), where 1«=i«=M and 1«=j«=N (step 814). This determination makes it also possible to select the index m' of the time-slot during which the maximum RSSI has been determined as it represents the index of the radiating element active at the server device during that time-slot. The index m' is then transmitted to the server (step 815), and when received at the server (step 803), is used in the communication phase for transmitting signals from the server to the client using narrow beams (step 806).

Steps 816 and 817 are similar to steps 714 and 717 of figure 7b.

In an equivalent way to step 706 of figure 7a, and in order to configure the reception path from the client to the server, a detecting element, DE(n'), that is adjacent to RE(m') is selected without further scanning process (step 804).

Finally, at step 805, beams m' and n', associated respectively with radiating element RE(m') and detecting element DE(n), are activated to be used during the communication phase at step 806.

Figure 9 is a flowchart of the algorithm executed by CPU 231 at the initialization of wireless transceiver 103 of video projector 104 (client) according to a third embodiment. This embodiment is an alternative to the flowchart of figure 7b as it shows a variant for the selection of an adjacent radiating element (step 714). It should be understood however that figure 7b has been chosen for illustration only and the described variant can also be implemented for selecting an adjacent radiating element, either at the client device or at the server device.

Steps 901, 902, 903, 906, 907 and 908 are respectively similar to steps 711, 712, 713, 715, 716 and 717 of figure 7b, and their description will not be repeated.

After a detecting element DE(nl) has been selected at step 903, an adjacent radiating element RE(m) is selected. In order to make the emitting beam m more accurately oriented in the direction of the received communication path, the selecting of the adjacent radiating element is based on the signal strength (power) detected on the sides of the detecting element ni. In fact, the received communication path is not necessarily centered towards the detecting element with maximum detected power (DE(nl)), but could point towards one of the sides of the detecting element ni, likely in the direction of an adjacent radiating element.

Steps 904 and 905 represent one possible implementation of the selecting of the adjacent radiating element based on the signal strength detected on the sides of the detecting element ni.

First, a second detecting element n2 (DE(n2)) is selected, among the two detecting elements surrounding DE(nl), which has the highest RSSI between the two surrounding elements (step 904). Then, the radiating element that is located between the detecting element ni and the detecting element n2 is selected as the radiating element m.

In other words, radiating element mis adjacent to both DE(nl) and DE(n2).

An alternative implementation of steps 904 and 905 (not illustrated) may for example rely on the selecting of a consecutive pair of detecting elements (DE(nl),DE(n2)) that has the highest cumulative power or strength among the consecutive pairs (DE(i),DE(j)) of detecting elements, and then the radiating element that is adjacent to both DE(nl) and DE(n2) is selected as the radiating element m.

Claims (11)

1. CLAIMS1. A transceiver comprising: an electromagnetic lens having a variation in permittivity along a predetermined plane for guiding electromagnetic signals along said predetermined plane; a plurality of radiating elements configured to radiate electromagnetic signals into the electromagnetic lens, the radiated electromagnetic signals being then guided by the electromagnetic lens; and a plurality of detecting elements configured to detect electromagnetic signals radiated out of the electromagnetic lens, the detected electromagnetic signals being guided by the electromagnetic lens prior their detecting therefrom; wherein the radiating elements are positioned in alternation lelatively to the detecting elements along the predetermined plane.
2. 2. The transceiver of claim 1, wherein adjacent radiating/detecting elements are kept close to each other with no gap between them.
3. 3. The transceiver of claim 1, wherein the plurality of radiating elements and the plurality of detecting elements are implemented using waveguides.
4. 4. The transceiver of claim 1, wherein the electromagnetic lens is a Luneburg lens with a refraction index of s(r) = 2 -r2, where r is the normalized radius.
5. 5. A method of configuring a transceiver for a communication with a remote device, the transceiver comprising an electromagnetic lens having a variation in permittivity along a predetermined plane for guiding electromagnetic signals along said predetermined plane, a plurality of radiating elements configured to radiate electromagnetic signals into the electromagnetic lens and a plurality of detecting elements configured to detect electromagnetic signals radiated out of the electromagnetic lens and positioned in alternation relatively to the radiating elements along the predetermined plane, the method comprising: determining a first element of the transceiver that radiates or detects electromagnetic signals when the transceiver is in communication in a first direction with the device; selecting a second element of the transceiver that is adjacent to the determined element; and activating the second element for communicating with the device in the reverse direction.
6. 6. The method of claim 5, wherein the first element is a detecting element and the second element is a radiating element.
7. 7. The method of claim 6, wherein the selecting of the second radiating element comprises: selecting a third detecting element associated with the highest signal strength detected among the detecting elements surrounding the first detecting element; and selecting as second radiating element the element that is adjacent to both the first detecting element and the third detecting element.
8. 8. The method of claim 5, wherein the communication in the first direction and the communication in the reverse direction are performed in half-duplex mode using a same frequency band.
9. 9. The method of claim 5, wherein the communication in the first direction and the communication in the reverse direction are performed in full-duplex mode using respectively distinct frequency bands.
10. 10. Program which, when executed by a computer or processor in a device, cause the device to carry out the method of claim 5.
11. 11. A transceiver substantially as hereinbefore described with reference to Figures 2 to 6aIb of the accompanying drawings.