Radiation pattern adaptable by obstacle polarization

Abstract

Radio frequency system comprising a main antenna and a radiation pattern matching device (6) comprising a printed circuit board (8) on which are printed two radiating elements (10) and a reflector (25), and on which is mounted a switching circuit (17) connected to the two radiating elements and arranged to be driven such that: - when the switching circuit is in a blocked mode, the radio frequency system (1) presents a first radiation pattern; - when the switching circuit is in a passing mode, the two radiating elements form a half-wave dipole antenna (18), the radio frequency system (1) then presenting a second radiation pattern having an increased or decreased gain in at least one predetermined direction.

Description

[0001] The invention relates to the field of equipment comprising radiofrequency systems, such as access points for example. BACKGROUND

[0002] The radiation pattern of an antenna depends on several parameters, such as the type of wave propagation it generates, the shape of the radiating element, its dimensions and the materials it is made of. Depending on the aforementioned parameters and the environment in which the antenna is located, a radiation pattern of a specific shape is created.

[0003] In the case of using the MIMO technique (for Multiple Input Multiple Output ), antennas can transmit and receive signals simultaneously. Thus, the combined radiation pattern of all correlated and decorrelated antennas is considered to determine the maximum power that can be transmitted or the minimum power that can be received, as well as the spatial coverage.

[0004] It is planned to equip an access point (WiFi access point for example) with such a MIMO system.

[0005] In access points, the combined radiation patterns are very often quasi-isotropic, i.e. in the shape of a sphere surrounding the equipment, because the objective is to radiate in all directions in order to have the best coverage and therefore to maintain good communication quality regardless of the position of the stations.

[0006] US regulations (see in particular the FCC rules (for Fédéral Communications Commission ), notably for the AFC (for Automated Frequency Coordination )) requires access point manufacturers, depending on their geographical position and the frequency of the transmission channel, to limit the power transmitted beyond a certain elevation above the horizon to 21 dBm, without affecting the power in other directions (36 dBm).

[0007] It therefore seems interesting to be able to act on the radiation pattern in at least one predefined direction to reduce or increase the gain of the antenna(s) used in said predefined direction(s).

[0008] This allows, for example, the radiation pattern of an antenna system to be modified to adapt it to the geographical area where the equipment incorporating said antenna system is used. This allows the same antenna system to be used in two regions with different regulations, without redesigning the system. This allows the antenna system to be configured so that it has a certain radiation pattern when marketed in the United States, and another radiation pattern when marketed in Europe.

[0009] The modification of the radiation pattern could also be carried out at the time of its installation at the user's premises, or be carried out in real time, during operation, to improve the efficiency of the communication if necessary.

[0010] Mechanical, electronic, and software techniques are known for modifying a radiation pattern.

[0011] Mechanical techniques require the integration of moving parts into the equipment. These moving parts are not very robust, complex, and expensive.

[0012] In the case of antenna systems of Wi-Fi, LTE, 5GNR radios, etc., the radiation pattern can be distorted in an arbitrary direction according to the method of beamforming by directly applying via software phase shifts between the signals sent to each antenna (for example by varying the N SS, i.e. the Number of Spatial Stream ) or by applying time delays (for example with the CDD method, for Cyclic Delay Diversity ), which increases the gain in the directions where the user is located, thus creating a minor perceptible distortion of the latter.

[0013] However, these techniques are highly dependent on the environment in which the communication is established, making the shape of the radiation patterns random and therefore uncontrollable.

[0014] For directional antenna systems, the solution of beamsteering, or radiation pattern shifting, implements a phased antenna array. It consists of several radiating elements connected together with a phased feed network or with variable phase shifters. Depending on the activated elements and the phase difference between the elements, the radiation pattern is more or less directional and oriented in a given direction.

[0015] The disadvantage is that this technique requires an array of multiple antennas, which takes up a lot of space at ISM band frequencies (Wi-Fi, LTE, etc.) and therefore makes its use impossible on Internet access gateways. OBJECT

[0016] One or more embodiments aim to adapt the radiation pattern of at least one antenna on command: without acting directly on this antenna, nor on the signals sent to it, nor on the radiofrequency components to which it is connected; without using any moving part; via a space-saving solution. SUMMARY

[0017] In order to achieve this aim, a radiofrequency system is proposed comprising a main antenna and a radiation pattern matching device comprising a printed circuit on which two radiating strands and a reflector are printed, and on which is mounted a switching circuit connected to the two radiating strands and arranged to be controlled so that: when the switching circuit is in a blocked mode, a current flow between the two radiating strands is blocked and the radiofrequency system has a first radiation pattern; when the switching circuit is in a passing mode, the current flow between the two radiating strands is not blocked so that the two radiating strands form a half-wave dipole antenna, the radiofrequency system then having a second radiation pattern having, relative to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0018] The radiation pattern matching device, positioned near the main antenna, can therefore be controlled to configure the radiation pattern of the radio frequency system according to the first radiation pattern or the second radiation pattern.

[0019] When the switching circuit is in the closed state (passing mode), the radiating strands and the reflector act as a passive, reflective antenna, which changes the directivity of the radio frequency system.

[0020] This solution therefore makes it possible to modify the radiation pattern without acting on the main antenna itself, nor on the signals it receives, nor on the radiofrequency components to which it is connected.

[0021] This solution requires a small footprint, because the radiation pattern matching device is small. The radiation pattern matching device does not require changing the position of a moving element to adapt the radiation pattern.

[0022] Further provided is a radio frequency system as previously described, wherein the main antenna extends in a first plane, and wherein the printed circuit of the radiation pattern matching device extends in a second plane perpendicular to the first plane.

[0023] We further propose a radiofrequency system as previously described, in which a first distance between the main antenna and the printed circuit, along a first axis belonging to the first plane and perpendicular to the second plane, is equal to X / 8, and in which a second distance between the main antenna and the printed circuit, along a second axis belonging to the second plane and perpendicular to the first axis, is equal to λ / 16.

[0024] Further provided is a radio frequency system as previously described, wherein a transmission coefficient between the main antenna and the radiation pattern matching device is between -15 dB and -6 dB.

[0025] We further propose a radiofrequency system as previously described, in which the two radiating strands extend successively along a length of the printed circuit, and in which the reflector comprises a main portion which extends over the entirety of said length.

[0026] A radio frequency system as previously described is further provided, wherein the reflector further comprises two secondary portions each extending from a separate end of the main portion while being perpendicular thereto.

[0027] We further propose a radiofrequency system as previously described, in which each radiating strand is connected to the switching circuit by a coplanar waveguide.

[0028] We further propose a radiofrequency system as previously described, in which: the radiating strands, the reflector, the coplanar waveguides and the switching circuit are located on a first layer of the printed circuit, the coplanar waveguides and the switching circuit being positioned in a central portion of the first layer, the radiating strands extending on either side of said central portion; the printed circuit comprises a main ground plane printed on a second layer of the printed circuit, the main ground plane being located in a central portion of the second layer; ground tracks of the coplanar waveguides, a ground plane of the switching circuit, as well as the reflector, being connected to the main ground plane.

[0029] Further provided is a radio frequency system as previously described, wherein the switching circuit comprises a single-pole, single-throw switch.

[0030] A radio frequency system as previously described is further provided, further comprising a one-piece support comprising a first part arranged to carry the main antenna and a second part arranged to carry the radiation pattern matching device, the second part being arranged to be able to manually insert and remove the radiation pattern matching device.

[0031] A radiofrequency system as previously described is further proposed, comprising a plurality of main antennas each associated with a separate radiation pattern matching device.

[0032] We further propose a radio frequency system as previously described, the main antennas being arranged to operate according to the MIMO technique.

[0033] We further propose equipment comprising a radiofrequency system as previously described.

[0034] We further propose equipment as previously described, the equipment being an access point.

[0035] We further propose a control method, implemented by a processing unit of equipment as previously described, and comprising the steps of: acquiring a command to configure a radiation pattern of the radiofrequency system according to the first radiation pattern or the second radiation pattern; producing a control voltage which depends on said command, and applying said control voltage to the input of the switching circuit.

[0036] A computer program is further provided comprising instructions which cause a processing unit of the equipment as previously described to execute the steps of the control method as previously described.

[0037] Further provided is a computer-readable recording medium on which the computer program as previously described is recorded.

[0038] The embodiment(s) will be better understood in light of the following description of particular non-limiting implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Reference will be made to the attached drawings, including: [ Fig. 1 ] there figure 1 represents an access point in which the radio frequency system is integrated; [ Fig. 2 ] there figure 2 represents two examples of a first radiation pattern and an associated second radiation pattern; [ Fig. 3 ] there figure 3 is a perspective view, from the front, of the main antenna and the radiation pattern matching device; [ Fig. 4 ] there figure 4 is a view similar to that of the figure 3 , but from the back; [ Fig. 5 ] there figure 5 is a view similar to that of the figure 3 , but aside; [ Fig. 6 ] there figure 6 represents the upper layer and the lower layer of the printed circuit of the radiation pattern matching device; [ Fig. 7 ] there figure 7 represents an electrical diagram of the radiation pattern matching device; [ Fig. 8 ] there figure 8 represents a graph comprising curves of the S parameters of the switching circuit with SPST switch, in the passing mode; [ Fig. 9 ] there figure 9 is a figure similar to the figure 8 , in blocked mode; [ Fig. 10 ] there figure 10 represents the magnetic field strength, electric field strength and far-field directivity, for different configurations of the main antenna and the radiation pattern matching device; [ Fig. 11 ] there figure 11 represents a graph comprising a curve of the reflection rate of the main antenna, a curve of the reflection rate of the PR antenna, and a curve of the transmission coefficient between the main antenna and the PR antenna; [ Fig. 12 ] there figure 12 represents sections of the radiation pattern according to different planes, corresponding to lines 2, 4 and 6 of table 1; [ Fig. 13 ] there figure 13 represents sections of the radiation pattern according to different planes, corresponding to the lines of table 2; [ Fig. 14 ] there figure 14 represents a diode switching circuit; [ Fig. 15 ] there figure 15 is a figure similar to the figure 8 , for the diode switching circuit; [ Fig. 16 ] there figure 16 is a figure similar to the figure 9 , for the diode switching circuit; [ Fig. 17 ] there figure 17 is a perspective view, from the side and from above, of the support and the radiation pattern matching device; [ Fig. 18 ] there figure 18 is a top view of the access point, without its top cover; [ Fig. 19 ] there figure 19 represent radiation patterns of the MIMO system at different frequencies and for different configurations of the states of the matching devices. DETAILED DESCRIPTION

[0040] In reference to the figure 1 , the radiofrequency system 1 is here integrated into the upper part of an access point 2 having a “tower” structure and which has a general cylindrical shape with axis A1.

[0041] Access point 2 is for example a Wi-Fi access point.

[0042] The radiofrequency system 1 here comprises an antenna system arranged to operate according to the MIMO technique.

[0043] Radiofrequency system 1 allows the shape of the radiation pattern of this MIMO system to be controlled using a circuit external to the antenna system. The control of the shape of the radiation pattern is achieved without intervening on the parameters of the radiofrequency components connected to the antenna system (chips, front-end modules (or FEM, for Front-End Modules ), etc.), nor on the antenna system itself. In particular, the control carried out does not consist of modifying the number of spatial streams, nor of defining the phase shift between the signals on each antenna, nor of using a precise number of antennas and choosing which antennas will transmit and receive.

[0044] Radiofrequency system 1 allows to create an attenuation or an increase in the gain of a single antenna or an antenna system in a specific direction, on command, with a polarization obstacle reflection system. This control does not affect the operation of the antenna system and does not intervene on the physical layers of the radio interface concerned, which are controlled by a processor and other electronic chips with specific algorithms.

[0045] The radiofrequency system 1 comprises a main antenna or a system of main antennas, and a radiation pattern matching device. It can, on command, have either a first radiation pattern, close to that of the antenna or the system of antennas, or a second radiation pattern, different from the first radiation pattern.

[0046] The modified radiation pattern has reduced or increased gain in at least one predetermined direction.

[0047] We see on the figure 2 access point 2 and two typical examples: of a first radiation pattern 3a, 3b, and of the associated second radiation pattern 4a, 4b.

[0048] We see that the first radiation patterns 3a, 3b are quasi-isotropic, while the second radiation patterns 4a, 4b present modified gains in certain directions.

[0049] As will be described, the radiofrequency system 1 allows: to obtain a radiation pattern having a shape close to that of the antenna(s) “alone”, when the radiation pattern matching device is deactivated; to distort the radiation pattern(s) without altering the efficiency of the antenna system, when the radiation pattern matching device is activated; to avoid moving parts; to control the radiation patterns over a wide frequency band.

[0050] The radiofrequency system 1 is now described in more detail. The radiofrequency system 1 comprises at least one main antenna (here four) and, for each main antenna, a radiation pattern matching device adapted to said main antenna.

[0051] In reference to the figures 3 à 7 , we are first of all interested in an assembly formed by a main antenna 5 and the associated radiation pattern adaptation device 6.

[0052] The main antenna 5 is a TRX antenna (transmitting and receiving antenna), of the patch antenna type. It has a flat, rectangular shape with a length L1 and a width l1.

[0053] We call À the wavelength corresponding to the central frequency of the bandwidth on which this main antenna 5 is intended to operate.

[0054] The central frequency is for example 5800 MHz.

[0055] When the access point 2, in which the radiofrequency system 1 is integrated, is positioned in its nominal operating position (i.e. placed on a flat and horizontal support), the main antenna 5 extends in a vertical plane while being oriented at an angle α = 45° (i.e. an axis A2, parallel to the length of the main antenna, forms an angle of 45° with a horizontal plane).

[0056] The radiation pattern matching device 6 comprises a printed circuit 8. Its substrate is here an FR4 substrate.

[0057] The printed circuit board 8 has a generally rectangular shape with cut corners.

[0058] The printed circuit board 8 has a length L2 and a width 12.

[0059] Two radiating strands 10 are printed on a first layer (here on the upper layer) of the printed circuit 8.

[0060] The two radiating strands 10 are each of generally rectangular shape, and extend successively along the length of the printed circuit 8.

[0061] The length L3 of each radiating strand 10 is here equal to λ / 4. λ / 4 is the quarter wavelength of the central frequency of the operating band of the main antenna.

[0062] Each radiating strand 10 is therefore a relatively wide printed track. The two radiating strands 10 each extend on either side of a central axis A3 of the printed circuit 8 extending along its width.

[0063] The side (width) of each radiating strand 10 closest to said axis A3 has a generally triangular shape (oriented towards the outside of the strand). A track 11 extends from the vertex 12 of said triangle then makes a right angle to extend parallel to said axis A3 in the direction of the edge 14 (length) of the printed circuit 8. Ground tracks 15 extend on each side of the track 11. The track 11 and its ground tracks 15 form a coplanar waveguide 16.

[0064] The 16 coplanar waveguides are 50 Q tracks.

[0065] The two sets, each formed by a radiating strand 10 and a coplanar waveguide 16, are arranged symmetrically with respect to the axis A3.

[0066] A switching circuit 17 is mounted on the printed circuit 8.

[0067] The switching circuit 17 can be controlled so that: when the switching circuit 17 is in an open state (blocked mode, OFF), a current flow between the two radiating strands 10 is blocked and the radiofrequency system 1 has a first radiation pattern; when the switching circuit 17 is in a closed state (passing mode, ON), the current flow between the two radiating strands 10 is not blocked so that the two radiating strands 10 form a half-wave dipole antenna 18, the radiofrequency system 1 then having a second radiation pattern having, compared to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0068] The switching circuit 17 is here a radio frequency SPST switch (SPST for Single Pole Single Throw , or single-pole, single-throw switch).

[0069] The SPST switch 17 comprises a first port 20 connected to the left radiating strand 10, a second port 21 connected to the right radiating strand 10, a third port 22 (power supply) and a fourth port 23 (control). The first port 20 and the second port 21 can therefore be selectively connected (closed state) or disconnected (open state), on command, via the fourth port 23.

[0070] When the control voltage Vc is equal to 0 V, the SPST switch 17 is in the open state. When the control voltage Vc is equal to 3.3 V, the SPST switch 17 is in the closed state.

[0071] The SPST switch 17 therefore makes it possible to establish or break an electromagnetic connection between the two radiating strands 10. In the closed state, it thus creates the half-wave dipole antenna 18. In the open state, it leaves the radiating strands 10 as very high frequency monopoles.

[0072] We have seen that the coplanar waveguides 16 are 50 Ω tracks. The SPST switch 17 therefore sees an impedance of 50 Ω at its input and output.

[0073] This is very advantageous. Indeed, the SPST 17 switch used is a standard component that has been designed for operation at 50 Ω (standard impedance for civilian radio frequency applications). Using a standard component is of course interesting from the point of view of the component cost, but also its availability.

[0074] The SPST 17 switch therefore works optimally: it passes the signal with minimal insertion loss and it blocks the signal with maximum attenuation.

[0075] If the coplanar waveguides 16 were not 50 Ω tracks, the SPST switch 17 would not be impedance matched and therefore its performance would be degraded.

[0076] We see on the figure 8 the S parameter curves for the SPST switch: Sij (curve C1), Sji (curve C2), Sii (first port return loss: curve C3), Sjj (second port return loss: curve C4), in on-mode. We see on the figure 9 the same curves, in blocked mode: curves C5, C6, C7, C8.

[0077] The printed circuit 8 further comprises a reflector 25 printed on the printed circuit 8. The reflector 25 comprises a main portion 26 which extends over the entire length of the printed circuit 8 along the edge 14. This main portion 26 itself comprises a central portion which rises towards the center of the printed circuit 8. The central portion of the reflector 25 is located in a central portion of the first layer, in which the guides 16 are also positioned. The radiating strands 10 extend on either side of said central portion.

[0078] The reflector 25 further comprises two secondary portions 27 which each extend from a separate end of the main portion 26 while being perpendicular to the latter.

[0079] The reflector 25 is therefore a track whose length is equal to that of the printed circuit board 8, and which is folded in a certain way on the ends, with a certain angle to increase the level of reflectivity. It should also be noted that the wider this track is, the more reflective it is. This design was thought out to satisfy a compromise between dimensions, complexity, volume and performance of the solution.

[0080] The printed circuit 8 further comprises a main ground plane 28 printed on a second layer (here on the lower layer of the printed circuit 8). The main ground plane 28 is positioned in a central portion of the second layer, superimposed with the central portion of the first layer.

[0081] The ground tracks 15 of the coplanar waveguides 16, the ground plane 29 of the SPST switch 17, as well as the reflector 25, are connected to the main ground plane 28.

[0082] The second layer of the printed circuit also comprises a track 30 connected to the third port 22 of the SPST switch 17 (power supply) and a track 31 connected to the fourth port 23 of the SPST switch 17. These two tracks 30, 31 each end with a rectangular portion 32, 33, having an edge coincident with the edge 14 of the printed circuit 8. A first cable 34, on which a supply voltage Vcc runs, is soldered to the portion 32. A second cable 35, on which a control voltage Vc runs, is soldered to the portion 33.

[0083] We see on the figures 6 And 7the decoupling capacitors 36 between the main ground plane 28 of the printed circuit 8 and the portion 32 (supply voltage), and between the main ground plane 28 and the portion 33 (control voltage).

[0084] The access point 2 has a motherboard 40 which includes radio frequency components. The main antenna 5 is connected to the motherboard via a coaxial cable 41 (50 Ω).

[0085] The first cable 34 and the second cable 35 are connected to the motherboard 8.

[0086] The motherboard 40 includes a power supply unit 42 and a processing unit 43.

[0087] The power supply unit 42 provides the supply voltage Vcc to the SPST switch 17 (via the first cable 34).

[0088] The processing unit 43 supplies the control voltage Vc to the SPST switch 17 (via the second cable 35). It is therefore the processing unit 43 which controls the evolution of the radiation pattern of the radiofrequency system (transition from the first radiation pattern to the second radiation pattern, and vice versa).

[0089] The processing unit 43 comprises at least one processing component 43a, which is for example a “generalist” processor, a processor specialized in signal processing (or DSP, for Digital Signal Processor ), a microcontroller, or a programmable logic circuit such as an FPGA (for Field Programmable Gate Arrays ) or an ASIC (for Application Spécifie Integrated Circuit ) .

[0090] The processing unit 43 further comprises one or more memories 43b, connected to or integrated in the processing component 43a. At least one of these memories 43b forms a computer-readable recording medium, on which is recorded at least one computer program comprising instructions which cause the processing component 43a to execute at least some of the steps of the following control method.

[0091] Processing unit 43: acquires an instruction intended to configure the radiation pattern of the radiofrequency system 1 according to the first radiation pattern or the second radiation pattern; produces a control voltage Vc which depends on said instruction, and applies said control voltage to the input of the switching circuit (here on the fourth port 23 of the SPST switch 17.

[0092] An optimal position of the main antenna 5 and the radiation pattern matching device 6 is now described.

[0093] The main antenna 5 extends in a first plane P1, and the printed circuit 8 extends in a second plane P2 perpendicular to the first plane P1.

[0094] The radiation pattern matching device 6 is therefore positioned perpendicularly above the main antenna 5.

[0095] A first distance d1 between the main antenna 5 and the printed circuit 8, along a first axis X1 passing through the first plane P1 and perpendicular to the second plane P2, is equal to λ / 8.

[0096] A second distance d2 between the main antenna 5 and the printed circuit 8, along a second axis X2 contained in the second plane and perpendicular to the second axis, is equal to λ / 16.

[0097] The radiation pattern matching device 6 is therefore spaced from the main antenna 5 by λ / 8 on the vertical plane and λ / 16 on the horizontal plane of a chosen frequency (by calculating the wavelength in free space with εr and µr equal to 1).

[0098] The main antenna 5 and the radiation pattern matching device 6 are connected to a common ground.

[0099] This common ground is also a ground of the access point 2. It includes a metal grid 45 belonging to the chassis of the access point 2.

[0100] For this purpose, the radiofrequency system 1 comprises a spring ground contact 46, which is fixed to the ground plane 28 of the printed circuit 8 and to the metal grid 45.

[0101] The operating principle of the radiofrequency system 1 is now described.

[0102] When the SPST switch 17 is in the open state (blocked mode), the flow of current between the two radiating strands 10 is blocked and the radiofrequency system 1 has a first radiation pattern, which is substantially that of the main antenna 5 alone (it is not perfectly identical due to the influence of the printed circuit and the tracks printed on it).

[0103] Indeed, even if the system is designed to reduce the occupied surface area as much as possible and so that the lengths of the conductive elements are different from the wavelengths of the useful frequencies when the system is in blocked mode, it still contains metallic conductive elements (strands 10, reflector 25, etc.), which causes the shape of the initial diagram to vary slightly (this depends on the frequencies).

[0104] When the SPST switch 17 is in the closed state (passing mode) and the main antenna 5 transmits or receives a radio frequency signal, i.e. an electromagnetic wave, the dipole antenna 18 formed on the printed circuit 8 of the radiation pattern matching device 6 partially receives the radio frequency signal transmitted by the main antenna 5.

[0105] We can then consider that the printed circuit 8 and its components behave like a passive antenna which we will call PR antenna (Passive Reflective Antenna).

[0106] By emitting an electromagnetic wave, the main antenna 5 generates an electric field E and a magnetic field H in the space around it with a more or less different mapping in accordance with its radiation pattern.

[0107] The electric field induces in this case a voltage in the PR antenna between its radiating strands 10, and the magnetic field induces a surface current on the same radiating conductive parts. This voltage and current flowing on the PR antenna then create an electromagnetic field, with a different spatial mapping governed by its radiation pattern. The combination of the electromagnetic fields generated by the main antenna and the PR antenna creates a combined radiation pattern with a particular shape oriented mainly in a predetermined direction. This phenomenon is completely passive. The design of the PR antenna, equipped with the reflector 25 printed on the printed circuit 8, increases the directivity of the combined radiation, because the received waves are reflected.

[0108] We see on the figure 10 the fields (magnetic field, electric field and far field) for the main antenna 5 without the radiation pattern matching device 6, with the radiation pattern matching device 6 in blocked mode, and with the radiation pattern matching device 6 in passing mode.

[0109] The magnetic field is maximum in the Z1 zones (greater than 1 A / m). The electric field is maximum in the Z2 zones (greater than 300 V / m).

[0110] It can be seen that with the radiation pattern matching device 6 in the pass mode, the gain of the radiation pattern increases towards the negative side of the X axis, and decreases in the other direction. Hole 47 is accentuated.

[0111] The radiofrequency system 1 then has a second radiation pattern having, relative to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0112] The reception efficiency of the PR antenna therefore depends on several factors, such as the distance between the antennas, the position of the two antennas, the relative orientation, the radiation characteristics of the main antenna as well as the dimensions and electrical properties of the PR antenna.

[0113] In this configuration, the PR antenna therefore essentially acts as a passive receiver and reflector that can capture part of the signal transmitted and / or received by the main antenna. It does not amplify or improve the quality of the signal.

[0114] It is noted that the proximity of the main antenna 5 and the radiation pattern matching device 6 modifies the characteristics of the main antenna 5, and this in a different way if the radiation pattern matching device 6 forms a reflective half-wave dipole antenna (switch: closed state) or if the metallic elements formed by the radiating strands are separated (switch: open state).

[0115] Reflection efficiency, energy losses and electromagnetic interactions between antennas were taken into account to achieve the desired performance.

[0116] In reference to the figure 11 , the reflection rate ( return loss ) of the main antenna 5 (curve C9) is low (less than -10dB) over a bandwidth wider than the useful bandwidth 48 (operating frequency band). This makes it possible to anticipate a frequency shift due to its proximity to the PR antenna and to avoid a drop in its efficiency which could deteriorate the performance of its radiation and which could deteriorate the performance of the access point 2 because of the excessively high conducted reflection level.

[0117] The return loss of the PR antenna (C10 curve) must also be low (less than -10dB) in the operating frequency band so that it can have the desired impact on the main antenna.

[0118] The transmission coefficient (curve C11) between the two antennas, i.e. the coupling, must not be too strong so as not to have too much of an impact on the efficiency of the main antenna 5 and must not be too weak to create a real distinction between the two closed / open states of the SPST switch 17.

[0119] If the original signal is already too weak, the isolation created by the SPST 17 switch is of little use.

[0120] Advantageously, the transmission coefficient between the main antenna 5 and the radiation pattern matching device 6 is between -15 dB and -6 dB.

[0121] Table 1 (Appendix 1) illustrates an example of behavior obtained for a radiofrequency system comprising a main antenna and the radiation pattern matching device.

[0122] The first column (from the left) corresponds to the first distance between the main antenna and the radiation pattern matching device (along the X1 axis). The fourth row (from the top) corresponds to the optimal position previously described.

[0123] The second column corresponds to the state of the SPST switch.

[0124] The third column gives the directivity values ​​for the three frequencies: 5180 MHz, 5500 MHz and 5800 MHz.

[0125] The fourth column gives the "relative" directivity offsets with respect to the switch state and position. The fifth column gives the efficiency and the sixth column the field components (in %).

[0126] We see on the figure 12 sections of the radiation pattern (directivity) obtained according to different planes; XZ, YZ and XY (the X, Y, Z axes are visible on the figure 5 ) .

[0127] Table 2 (Appendix 2) is a similar table to Table 1, except that this time, in the first column, it is the inclination of the radiation pattern matching device 6 that varies.

[0128] We see on the figure 13 sections of the radiation pattern obtained according to different planes; XZ, YZ and XY.

[0129] It has been indicated here that the switching circuit, i.e. the polarizing element of the receiving / reflecting device, is an SPST switch.

[0130] Several other solutions are possible for passing or blocking a radio frequency signal in electronics, such as circuits based on diodes, CMOS MEMs, circulators and RF switches.

[0131] The switching circuit therefore does not necessarily include an SPST switch.

[0132] However, several of the possible alternatives have disadvantages that are difficult to circumvent in the intended application because of the charged radiofrequency environment, that is to say because of the concentration of waves in a restricted volume which creates electric fields inducing voltages on charged metallic elements and magnetic fields which create surface currents in a random manner on these same metallic elements.

[0133] The switching circuit can for example be a diode switching circuit.

[0134] In reference to the figure 14 , the switching circuit 50 comprises a first capacitor 51 having a first terminal connected to the radiating strands 10 and to the reflector 25, a first inductor 52 having a first terminal connected to the second terminal of the first capacitor 51 and a second terminal connected to the electrical ground. The cathode of the diode 53 is connected to the second terminal of the first capacitor 51 (and to the first terminal of the first inductor 52). The anode of the diode 53 is connected to a first terminal of the second capacitor 54. The second terminal of the second capacitor 54 is connected to the common ground of the equipment.

[0135] The circuit further comprises a second inductor 55 connected in series with a resistor 56 and a voltage source 57. The second inductor 55 has a first terminal connected to the anode of the diode 53 and a second terminal connected to the resistor 56.

[0136] This circuit has some disadvantages: relatively high cost, difficulty in finding commercially available radio frequency diodes with very low capacitance covering a wide frequency band and supporting high input power.

[0137] Furthermore, it is difficult to control the bias voltage of diode 53 on a circuit very close to several antennas transmitting at a power greater than 20 dBm. The risk with this type of assembly is that diode 53 is permanently biased, and therefore either permanently on or off, which cancels the desired function.

[0138] We see on the figure 15 the S parameter curves for the diode switching circuit 50: Sij (curve C12), Sji (curve C13), Sii (port 1 return loss: curve C14), Sjj (port 2 return loss: curve C15), in on-mode. We see on the figure 16 the same curves, in blocked mode: curves C16, C17, C18, C19.

[0139] In addition to the previously mentioned constraints related to the use of diodes, by comparing the figures 8 , 9 And 15, 16 , it is clearly visible that the insertion losses are higher on the 50 diode circuit (almost 3 dB in the middle of the useful band, i.e. almost 50% of the signal power passing through the circuit is lost) and the isolation is around 23 dB, which is not optimal compared to the 17 SPST switch whose insertion losses are at 0.7 max and the isolation is 10dB higher (34dB).

[0140] The SPST 17 switch, moreover, is easily found commercially. Its characteristics are known and more interesting for the present application. This component acts as a switch that can allow a radio frequency signal to pass with a low insertion loss or block it with an isolation around 30dB on the 5 to 6GHz band. It can support a maximum input power of 30dBm, which is more than sufficient.

[0141] We are now interested, with reference to the figure 17 , to the mechanical integration of the radiation pattern matching device 6.

[0142] The main antenna 5 and the radiation pattern matching device 6 are mounted on the same support 60 made of plastic (in one piece).

[0143] The support 60 comprises a first part 61 for receiving the main antenna and holding it in the position as shown in the figures 3 à 5 .

[0144] The support 60 comprises a second part 62 for accommodating the radiation pattern adaptation device.

[0145] The second part comprises a flat surface 63, of generally rectangular shape, having substantially the same dimensions as the printed circuit 8. The second part 62 also comprises a set of tabs each comprising a first portion which extends perpendicular to the flat surface 63 and from an edge thereof, and a second portion which extends perpendicular to the first portion and towards the inside of the flat surface 63.

[0146] The set of tabs comprises, for the edge 64 (length of the flat surface) of the flat surface, a tab 65 located approximately in the center of said edge and of reduced length, a tab 66 located close to the edge 67 (width of the flat surface 63), also of reduced length. The set of tabs also comprises a tab 68 which extends over the entire length of the edge 69 (width of the flat surface) and which extends over a portion of the length of the edge 70 (length of the flat surface) close to half of the latter.

[0147] A flexible finger 71, comprising a flat running portion, is defined in the thickness of the flat surface 63. The finger 71 has one end fixed to the flat surface 63 and a free end from which extends a hook 72 which projects perpendicular to the flat surface 63 at the edge 67.

[0148] The radiation pattern matching device 6 is manually installed in the support 60 in the following manner. The printed circuit 8 is inserted into the support 60 by being introduced through the edge 67 of the flat surface 63, and by pressing on the hook 72. The printed circuit 8 slides into the space formed between the flat surface 63 and the second portions of the tabs. When it is fully inserted, the hook 72 is no longer pressed in and projects at the edge 75 of the printed circuit 8 outside of it and pressing against it, which holds the printed circuit 8 in place. The insertion of the printed circuit 8 into the support is therefore achieved via a sliding connection (achieved by means of the tabs), and its retention is achieved via an elastic fitting (achieved by the flexible finger 71).

[0149] The radiation pattern matching device 6 can therefore be inserted into its holder and removed manually.

[0150] In reference to the figure 18 , the access point 2 comprises a plurality of radiofrequency systems 1 as previously described, the main antennas 5 of said radiofrequency systems being arranged to operate according to the MIMO technique.

[0151] Here, the access point has four radio frequency systems 1.

[0152] We see that the support 60 previously mentioned has an octagonal shape. It carries the four main antennas 5 and the four radiation pattern adaptation devices 6.

[0153] The plastic support 60 comprises four large faces 81 and four small faces 82 connecting said large faces 81.

[0154] Each radiofrequency system 1, comprising a main antenna 5 and a radiation pattern matching device 6, is associated with a separate large face 81. For each large face 81, the support 60 is arranged so that the main antenna 5 extends outside the support 60 while being oriented at 45° and being pressed against the external wall of said large face 81, while the radiation pattern matching device 6 is located inside the support 60 (the edge 64 of the flat surface 63 runs along the internal wall of said large face 81).

[0155] Table 3 of Appendix 3 lists different cases, each corresponding to a distinct combination of the modes of the radiation pattern matching devices.

[0156] For example, case 0 corresponds to a case where the radiation pattern matching devices are not mounted, case 1 corresponds to a case where the radiation pattern matching devices are mounted but are all in the blocked mode, and case 3 corresponds to a case where the matching devices are mounted and are all in the passing mode.

[0157] Note that, for Table 3, the NHPRP parameters ( Near Field Horizontal Partial Radiated Power ) at + / -45° and + / -30° were calculated using the following equations (equations B.11 and B.12 of section B.3.2 of CTIA v3.8.): NHPRP 45 = 1 4 π ∫ θ = π / 4 3 π / 4 ∫ Φ = 0 2 π EiRP θ θ Φ + EiRP Φ θ Φ sin θ d θ d Φ NHPRP 30 = 1 4 π ∫ θ = π / 3 2 π / 3 ∫ Φ = 0 2 π EiRP θ θ Φ + EiRP Φ θ Φ sin θ d θ d Φ

[0158] We see on the figure 19 , for the frequencies 2437 MHz, 5500 MHz and 5800 MHz, the associated resulting radiation patterns. For example, for case 3 at 5800 MHz, the increase in gain in the direction of the Y axis (in both directions) is clearly distinguished.

[0159] Of course, the different embodiments are not limited to the embodiments and examples described but include all variants falling within the scope of the invention.

[0160] In other examples, the characteristics of the reflector are such that the reflector is adapted to control the radiation pattern of the main antenna for different center frequencies respectively associated with different operating bands, such as the operating bands included in the so-called "6 GHz" band of the Wi-Fi 6E protocol.

[0161] The reflector could have a different shape, for an even higher level of reflectivity.

[0162] It is also possible to expand the printed circuit board to add a series of reflectors (to obtain a Yagi antenna type antenna for example) in order to increase the natural directivity of the half-wave dipole radiation pattern.

[0163] The corners of the radiation pattern matching device PCB are not necessarily cut out.

[0164] It has been described that the main antenna is positioned in a vertical plane by being oriented so as to form an angle of 45° with a horizontal plane. The radio frequency system can be implemented regardless of the position and orientation of the main antenna. The optimized position of the radiation pattern matching device with respect to the main antenna, which was described earlier, is a relative position with respect to the position and orientation of the antenna.

[0165] All numerical values ​​provided are examples. The main antenna frequency, for example, could be different from the frequencies listed here.

[0166] The radio frequency system may include any number of main antennas.

[0167] The shape of the access point could be different. For example, it could be a cylindrical shape with a rectangular or square cross-section, possibly with rounded corners.

[0168] The radio frequency system can be integrated into any type of equipment that implements radio frequency communication. ANNEXES Appendix 1: Table 1

[0169] Table 1 is divided here into two tables: 1A, 1B (which form the same table) tableau 1A Etat Directivité totale (dB) Offset Directivité Totale (dB) Efficacité (dB) 5180 MHz 5500 MHz 5800 MHz 5180 MHz 5500 MHz 5800 MHz 5180 MHz 5500 MHz 5800 MHz Relative switch mode Relative Position Relative switch mode Relative Position Relative switch mode Relative Position +10 mm ON 5 5.6 5.6 -1 1.3 -0.5 0.7 0 0.8 -0.36 -0.26 -0.34 OFF 6 6.1 5.6 -1.4 -0.9 0.2 -0.31 -0.27 -0.43 +5 mm ON 5.5 6 5.5 -0.3 0.8 0 0.3 0.1 0.9 -0.53 -0.35 -0.53 OFF 5.8 6 5.4 -1.2 -0.8 0.4 -0.32 -0.31 -0.53 Initial Position 0 mm ON 6.3 6.3 6.4 17 1.1 0.6 -1.58 -0.74 -0.65 OFF 4.6 5.2 5.8 -0.3 -0.38 -0.81 -5 mm ON 5.4 5.4 4.6 0.5 0.9 0.7 0.9 -0.8 18 -1.98 -0.7 -0.6 OFF 4.9 4.7 5.4 -0.3 0.5 0.4 -0.36 -0.49 -1.36 -10 mm ON 5.6 4.8 5.5 1 0.7 0.3 1.5 -0.3 0.9 -0.57 -0.33 -0.44 OFF 4.6 4.5 5.8 0 0.7 0 -0.39 -0.49 -1.27 tableau 1B Table 1B below includes columns normally positioned to the right of Table 1A (so, for the frequency 5180 MHZ, the values ​​50.7 and 49.3 are associated with the line “+ 10 mm ON”, the values ​​55 and 45 are associated with the line “+ 10 mm OFF”, etc. Polarization 5180 MHz 5500 MHz 5800 MHz Eθ Eφ Eθ Eφ Eθ Eφ 50.7 49.3 51.5 48.5 54.4 45.6 55 45 55.4 44.6 55.6 44.4 51.2 48.8 50.4 49.6 51.7 48.3 53.6 46.4 54.8 45.6 55.5 44.5 53.3 46.7 51.5 48.5 52.0 48.0 52.3 47.7 52.9 47.1 55.5 44.5 58.2 41.8 54.6 45.4 53.4 46.6 53.5 46.5 52.4 47.6 56.5 43.5 55.8 44.2 54.6 45.4 54.1 45.9 58.3 41.7 58 42 58.6 41.4 Appendix 2: Table 2 State Total Directivity (dB) Total Directivity Offset (dB) Efficiency (dB) Polarization 5180 MHz 5500 MHz 5800 MHz 5180 MHz 5500 MHz 5800 MHz 5180 MHz 5500 MHz 5800 MHz 5180 MHz 5500 MHz 5800 MHz Relative switch mode Relative Position Relative switch mode Relative Position Relative switch mode Relative Position Eθ Eϕ Eθ Eϕ Eθ Eϕ Tilt +30° ON 6 62 6 0.4 -0.3 0.6 -0.1 0.6 -0.4 -0.33 -0.26 -0.36 51.2 48.8 50.7 49.3 53.1 46.9 OFF 5.6 5.6 5.4 1 0.4 -0.4 -0.22 -0.2 -0.3 52.7 47.3 52.2 47.8 54.4 45.6 Initial Position 0 mm ON 6.3 6.3 6.4 1.7 1.1 0.6 -1.58 -0.74 -0.65 53. 3 46. 7 51.5 48.5 52. 2 47.8 OFF 4.6 5.2 5.8 -0.3 -0.38 -0.81 52. 3 47. 7 52.9 47.1 55. 5 44.5 Tilt -30° ON 6.5 67 6.4 16 0.2 0.75 0.4 1 0 -1.24 -0.56 -0.54 52.1 47.9 52.5 47.5 52.6 47.4 OFF 4.9 5.95 5.4 0.3 0.75 -0.4 -0.34 -0.71 -1 52.7 47.3 53 47 52.8 47.2 Appendix 3: Table 3 Case Switch Mode Gain (dBi) NHPRP (%) Switch 1 Switch 2 Switch 3 Switch 4 ANT1 ANT2 ANT3 ANT4 UGC + / - 45° + / - 30° 0 NM NM NM NM 5 5.5 5.3 5.6 2.3 70 50 1 OFF OFF OFF OFF 4.9 5.4 5.1 5.2 2.3 69 50 2 OFF ON OFF OFF 4.5 6.6 5.1 5.1 2.2 76 54 3 ON ON ON ON 6.9 6.6 6.9 6.4 2.2 80 58 4 ON ON OFF OFF 6.9 6.6 5.1 5.1 2.3 77 56 5 ON ON ON OFF 6.9 6.5 6.9 5.1 2.45 78 57

Claims

1. Radiofrequency system (1) comprising a main antenna (5) and a radiation pattern matching device (6) comprising a printed circuit (8) on which two radiating strands (10) and a reflector (25) are printed, and on which is mounted a switching circuit (17) connected to the two radiating strands and arranged to be controlled so that: - when the switching circuit is in a blocked mode, a flow of current between the two radiating strands (10) is blocked and the radiofrequency system (1) has a first radiation pattern;- when the switching circuit is in a passing mode, the flow of current between the two radiating strands (10) is not blocked so that the two radiating strands form a half-wave dipole antenna (18), the radiofrequency system (1) then having a second radiation pattern having, compared to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.; 2. Radiofrequency system according to claim 1, in which the main antenna (5) extends in a first plane (PI), and in which the printed circuit (8) of the radiation pattern matching device (6) extends in a second plane (P2) perpendicular to the first plane (P1).

3. Radiofrequency system according to claim 2, in which a first distance (d1) between the main antenna (5) and the printed circuit (8), along a first axis (X1) belonging to the first plane and perpendicular to the second plane, is equal to λ / 8, and in which a second distance (d2) between the main antenna and the printed circuit, along a second axis (X2) belonging to the second plane and perpendicular to the first axis, is equal to λ / 16.

4. Radiofrequency system according to one of the preceding claims, in which a transmission coefficient between the main antenna (5) and the radiation pattern matching device (6) is between -15 dB and -6 dB.

5. Radiofrequency system according to one of the preceding claims, in which the two radiating strands (10) extend successively along a length of the printed circuit (8), and in which the reflector (25) comprises a main portion (26) which extends over the entirety of said length.

6. Radiofrequency system according to claim 5, wherein the reflector (25) further comprises two secondary portions (27) which each extend from a separate end of the main portion while being perpendicular thereto.

7. Radiofrequency system according to one of the preceding claims, in which each radiating strand (10) is connected to the switching circuit (17) by a coplanar waveguide (16).

8. Radiofrequency system according to claim 7, wherein: - the radiating strands (10), the reflector (25), the coplanar waveguides (16) and the switching circuit (17) are located on a first layer of the printed circuit (8), the coplanar waveguides and the switching circuit being positioned in a central portion of the first layer, the radiating strands (10) extending on either side of said central portion; - the printed circuit comprises a main ground plane (28) printed on a second layer of the printed circuit, the main ground plane being located in a central portion of the second layer; - ground tracks (15) of the coplanar waveguides (16), a ground plane (29) of the switching circuit (17), as well as the reflector (25), being connected to the main ground plane (28).

9. Radiofrequency system according to one of the preceding claims, in which the switching circuit comprises a single-pole, single-throw switch (17).

10. Radiofrequency system according to one of the preceding claims, further comprising a support (60) in one piece comprising a first part (61) arranged to carry the main antenna (5) and a second part (62) arranged to carry the radiation pattern adaptation device (6), the second part (62) being arranged to be able to manually insert and remove the radiation pattern adaptation device (6).

11. Radiofrequency system according to one of the preceding claims, comprising a plurality of main antennas (5) each associated with a separate radiation pattern adaptation device (6).

12. Radiofrequency system according to claim 11, the main antennas being arranged to operate according to the MIMO technique.

13. Equipment comprising a radiofrequency system according to one of the preceding claims.

14. Equipment according to claim 13, the equipment being an access point.

15. Control method, implemented by a processing unit (43) of equipment according to one of claims 13 or 14, and comprising the steps of: - acquiring a setpoint aimed at configuring a radiation pattern of the radiofrequency system according to the first radiation pattern or the second radiation pattern; - producing a control voltage which depends on said setpoint, and applying said control voltage to the input of the switching circuit.

16. Computer program comprising instructions which cause a processing unit of the equipment according to one of claims 13 or 14 to execute the steps of the control method according to claim 15.

17. Computer-readable recording medium, on which the computer program according to claim 16 is recorded.

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