RADIATION DIAGRAM ADJUSTABLE BY OBSTACLE PRE-CALL

Description

[0001] The invention relates to the field of equipment comprising radio frequency 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 ), the antennas can transmit and receive signals simultaneously. Thus, the combined radiation pattern of all correlated and uncorrelated antennas is considered in order to determine the maximum power that can be transmitted or the minimum power that can be received, as well as the spatial coverage.

[0004] We are considering equipping an access point (e.g., a WiFi access point) with such a MIMO system.

[0005] In access points, combined radiation patterns are very often quasi-isotropic, that is to say 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] American regulations (see in particular the FCC rules (for Federal Communications Commission ), particularly for the AFC (for Automated Frequency Coordination )) requires manufacturers of access points, depending on their geographical location and the frequency of the transmission channel, to limit to 21 dBm the transmitted power beyond a certain elevation relative to the horizon, without calling into question the power in other directions (36 dBm).

[0007] It therefore seems advantageous 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 that antenna system is used. The same antenna system can thus be used in two regions with different regulations without redesigning the system. For instance, the antenna system could be configured to have a certain radiation pattern when sold in the United States and a different radiation pattern when sold in Europe.

[0009] The radiation pattern could also be modified at the time of installation at the user's premises, or in real time, during operation, to improve communication efficiency 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 for Wi-Fi, LTE, 5GNR, etc. radios, the radiation pattern can be distorted in an arbitrary direction according to the method of beamforming by directly applying phase shifts between the signals sent to each antenna via software (for example by varying the N SS, i.e. the Number of Spatial Stream ) or by applying time limits (for example with the fixed-term contract method, for Cyclic Delay Diversity ) , This increases the gain along the directions in which the user is located, thus creating a minor perceptible distortion of the user.

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

[0014] For directional antenna systems, the solution of beamsteering, Radiation pattern shifting, or pointing pattern shifting, employs a phased antenna array. This 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 them, the radiation pattern is more or less directional and pointed in a given direction.

[0015] The drawback is that this technique requires a network of several antennas, which takes up a lot of space at frequencies in the ISM band (Wi-Fi, LTE...) and therefore makes its use impossible on Internet access gateways.

[0016] US 2007 / 152893 A1, US 2006 / 044205 A1, US 2009 / 046019 A1, US 2005 / 035910 A1 and US 2010 / 231451 A1 disclose radio frequency systems comprising a main antenna and a passive radiation pattern matching device, said passive matching device comprising a reflector and a pair of radiating elements connected to a switching circuit. OBJECT

[0017] One or more embodiments are intended to adapt the radiation pattern of at least one antenna on demand: without acting directly on this antenna, nor on the signals sent to it, nor on the radio frequency components to which it is connected; without using a moving part; via a compact solution. SUMMARY

[0018] To achieve this goal, a radio frequency system is proposed comprising a main antenna and a radiation pattern matching device including a printed circuit board on which two radiating elements and a reflector are printed, and on which is mounted a switching circuit connected to the two radiating elements and arranged to be controlled such that: When the switching circuit is in a blocked mode, current flow between the two radiating elements is blocked and the radio frequency system exhibits a first radiation pattern; when the switching circuit is in a passing mode, current flow between the two radiating elements is not blocked so that the two radiating elements form a half-wave dipole antenna, the radio frequency system then exhibiting a second radiation pattern having, relative to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0019] The main antenna extends in a foreground plane, and the printed circuit board of the radiation pattern matching device extends in a second plane perpendicular to the foreground plane.

[0020] 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.

[0021] When the switching circuit is in the closed state (passing mode), the radiating strands and the reflector act as a passive and reflective antenna, which modifies the directivity of the radio frequency system.

[0022] 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 radio frequency components to which it is connected.

[0023] This solution requires minimal space, as the radiation pattern matching device is small. The radiation pattern matching device does not require changing the position of a moving element to adjust the radiation pattern.

[0024] We further propose a radio frequency system as previously described, in which a first distance between the main antenna and the printed circuit board, along a first axis belonging to the first plane and perpendicular to the second plane, is equal to A / 8, and in which a second distance between the main antenna and the printed circuit board, along a second axis belonging to the second plane and perpendicular to the first axis, is equal to λ / 16.

[0025] We also propose a radio frequency system as previously described, in which a transmission coefficient between the main antenna and the radiation pattern matching device is between -15 dB and -6 dB.

[0026] We also propose a radio frequency system as previously described, in which the two radiating strands extend successively along a length of the printed circuit board, and in which the reflector includes a main portion which extends over the entire length of said length.

[0027] We also propose a radio frequency system as previously described, in which the reflector further comprises two secondary portions which each extend from a distinct end of the main portion and are perpendicular to it.

[0028] We also propose a radio frequency system as previously described, in which each radiating strand is connected to the switching circuit by a coplanar waveguide.

[0029] We also propose a radio frequency system as previously described, in which: The radiating strands, reflector, coplanar waveguides and switching circuit are located on a first layer of the printed circuit board, the coplanar waveguides and 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 board includes a main ground plane printed on a second layer of the printed circuit board, 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, and the reflector, being connected to the main ground plane.

[0030] We also propose a radio frequency system as previously described, in which the switching circuit includes a unipolar unidirectional switch.

[0031] We also propose a radio frequency system as previously described, further comprising a one-piece support including 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 allow manual insertion and insertion of the radiation pattern matching device.

[0032] We also propose a radio frequency system as previously described, comprising a plurality of main antennas each associated with a separate radiation pattern matching device.

[0033] We also propose a radio frequency system as previously described, with the main antennas arranged to operate according to the MIMO technique.

[0034] We also offer equipment including a radio frequency system as previously described.

[0035] We also propose equipment as previously described, the equipment being an access point.

[0036] We also propose a control method, implemented by a processing unit of equipment as previously described, and comprising the following steps: acquire a command to configure a radiation pattern of the radio frequency system according to the first radiation pattern or the second radiation pattern; produce a control voltage that depends on said command, and apply said control voltage to the input of the switching circuit.

[0037] We also propose a computer program comprising instructions which lead a processing unit of the equipment as previously described to execute the steps of the piloting process as previously described.

[0038] In addition, a computer-readable recording medium is proposed, on which the computer program as previously described is recorded.

[0039] The embodiment(s) will be better understood in light of the following description of particular, non-limiting implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Reference will be made to the attached drawings, among which: [ 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 a second associated 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 rear; Fig. 5 ] there figure 5 is a view similar to that of the figure 3 , but from the side; Fig. 6 ] there figure 6 represents the top and bottom layers of the printed circuit board 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 SPST switching circuit, in the forward-biased mode; Fig. 9 ] there figure 9 is a figure similar to the figure 8 , in locked mode; [ Fig. 10 ] there figure 10 represents the intensity of the magnetic field, the electric field, and the 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 main antenna's reflection rate, a curve of the PR antenna's reflection rate, and a curve of the transmission coefficient between the main antenna and the PR antenna; Fig. 12 ] there figure 12 represents cross-sections of the radiation diagram along different planes, corresponding to rows 2, 4 and 6 of Table 1; [ Fig. 13 ] there figure 13 represents cross-sections of the radiation diagram along different planes, corresponding to the rows 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, side, and top view of the radiation pattern matching support and 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 diagrams of the MIMO system at different frequencies and for different configurations of the states of the adaptive devices. DETAILED DESCRIPTION

[0041] With reference to the figure 1 , the radio frequency 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.

[0042] Access point 2, for example, is a Wi-Fi access point.

[0043] The radio frequency system 1 here includes an antenna system arranged to operate according to the MIMO technique.

[0044] Radio frequency system 1 allows control of the radiation pattern shape of this MIMO system using a circuit external to the antenna system. Control of the radiation pattern shape is achieved without altering the parameters of the radio frequency components connected to the antenna system (chips, front-end modules (or FEMs, for Front-End Modules ), etc.), nor on the antenna system itself. In particular, the control performed does not consist of modifying the number of spatial fluxes, 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.

[0045] Radio frequency system 1 allows for the creation of attenuation or gain enhancement of a single antenna or an antenna system in a specific direction, on command, using a polarization-based obstacle reflection system. This control does not affect the operation of the antenna system and does not intervene in the physical layers of the radio interface in question, which are controlled by a processor and other electronic chips with specific algorithms.

[0046] The radio frequency system 1 comprises a main antenna or a system of main antennas, and a radiation pattern matching device. It can, on command, present either a first radiation pattern, close to that of the antenna or antenna system, or a second radiation pattern, different from the first radiation pattern.

[0047] The modified radiation pattern exhibits reduced or increased gain in at least one predetermined direction.

[0048] We can see on the figure 2 Access point 2 and two typical examples: of a first radiation diagram 3a, 3b, and of the second associated radiation diagram 4a, 4b.

[0049] We see that the first radiation diagrams 3a, 3b are almost isotropic, while the second radiation diagrams 4a, 4b show modified gains in certain directions.

[0050] As will be described, the radio frequency system 1 allows: to obtain a radiation pattern with a shape close to that of the "alone" antenna(s) 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 drive the radiation patterns over a wide frequency band.

[0051] We now describe in more detail the radio frequency system 1. The radio frequency system 1 includes at least one main antenna (here four) and, for each main antenna, a radiation pattern matching device adapted to said main antenna.

[0052] With reference to figures 3 à 7 , we are first interested in an assembly formed by a main antenna 5 and the associated radiation pattern matching device 6.

[0053] The main antenna 5 is a TRX antenna (transmit and receive antenna), of the patch antenna type. It has a flat, rectangular shape with a length L1 and a width l1.

[0054] We call λ the wavelength corresponding to the center frequency of the bandwidth on which this main antenna 5 is intended to operate.

[0055] The center frequency is, for example, equal to 5800 MHz.

[0056] When the access point 2, in which the radio frequency 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 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).

[0057] The radiation pattern matching device 6 includes a printed circuit board 8. Its substrate here is an FR4 substrate.

[0058] Printed circuit board 8 has a general rectangular shape with cut-out corners.

[0059] Printed circuit board 8 has a length L2 and a width l2.

[0060] Two radiating strands 10 are printed on a first layer (here on the top layer) of the printed circuit 8.

[0061] The two radiating strands 10 are each generally rectangular in shape, and extend successively along the length of the printed circuit 8.

[0062] The length L3 of each radiating element 10 is here equal to λ / 4. λ / 4 is the quarter wavelength of the center frequency of the operating band of the main antenna.

[0063] Each radiating element 10 is therefore a relatively wide printed track. The two radiating elements 10 extend on either side of a central axis A3 of the printed circuit 8, extending along its width.

[0064] The side (width) of each radiating element 10 closest to said axis A3 has a general triangular shape (oriented outwards from the element). A track 11 extends from the vertex 12 of said triangle and then makes a right angle to extend parallel to said axis A3 towards the edge 14 (length) of the printed circuit board 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.

[0065] The 16 coplanar waveguides are 50 Ω tracks.

[0066] The two assemblies, each formed by a radiating strand 10 and a coplanar waveguide 16, are arranged symmetrically with respect to the axis A3.

[0067] A switching circuit 17 is mounted on the printed circuit board 8.

[0068] The switching circuit 17 can be controlled so that: when the switching circuit 17 is in an open state (blocked mode, OFF), current flow between the two radiating elements 10 is blocked and the radio frequency system 1 presents a first radiation pattern; when the switching circuit 17 is in a closed state (passive mode, ON), current flow between the two radiating elements 10 is not blocked so that the two radiating elements 10 form a half-wave dipole antenna 18, the radio frequency system 1 then presenting a second radiation pattern having, compared to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0069] The switching circuit 17 is here a radio frequency SPST switch (SPST for Single Pole Single Throw, or unidirectional single-pole switch).

[0070] The SPST 17 switch comprises a first port 20 connected to the left radiating element 10, a second port 21 connected to the right radiating element 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) via the fourth port 23.

[0071] When the control voltage Vc is equal to 0 V, the SPST 17 switch is in the open state. When the control voltage Vc is equal to 3.3 V, the SPST 17 switch is in the closed state.

[0072] The SPST switch 17 therefore makes it possible to establish or break an electromagnetic link between the two radiating elements 10. In the closed state, it thus creates the half-wave dipole antenna 18. In the open state, it leaves the radiating elements 10 as very high frequency monopoles.

[0073] 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.

[0074] This is very advantageous. Indeed, the SPST 17 switch used is a standard component designed for operation at 50 Ω (the standard impedance for civilian radio frequency applications). Using a standard component is beneficial not only in terms of cost but also in terms of availability.

[0075] The SPST 17 switch therefore works optimally: it passes the signal with minimal insertion loss and blocks the signal with maximum attenuation.

[0076] 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.

[0077] We can see on the figure 8 The curves of the S parameters 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. This can be seen on the figure 9 the same curves, in locked mode: curves C5, C6, C7, C8.

[0078] The printed circuit board 8 further includes a reflector 25 printed on the printed circuit board 8. The reflector 25 includes a main portion 26 which extends along the entire length of the printed circuit board 8 along the edge 14. This main portion 26 itself includes a central part which rises towards the center of the printed circuit board 8. The central part 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.

[0079] The reflector 25 further comprises two secondary portions 27 which each extend from a distinct end of the main portion 26 and are perpendicular to it.

[0080] The reflector 25 is therefore a trace whose length is equal to that of the printed circuit board 8, and which is folded in a specific way at the ends, at a certain angle to increase the level of reflectivity. It should also be noted that the wider this trace, the more reflective it is. This design was conceived to satisfy a compromise between dimensions, complexity, volume, and performance of the solution.

[0081] The printed circuit board 8 further includes a main ground plane 28 printed on a second layer (here on the lower layer of the printed circuit board 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.

[0082] The ground tracks 15 of the coplanar waveguides 16, the ground plane 29 of the SPST switch 17, and the reflector 25, are connected to the main ground plane 28.

[0083] The second layer of the printed circuit board also includes a trace 30 connected to the third port 22 of the SPST switch 17 (power supply) and a trace 31 connected to the fourth port 23 of the SPST switch 17. These two traces 30, 31 each terminate in a rectangular portion 32, 33, having one edge coincident with the edge 14 of the printed circuit board 8. A first cable 34, carrying a supply voltage Vcc, is soldered to the portion 32. A second cable 35, carrying a control voltage Vc, is soldered to the portion 33.

[0084] We see on the figures 6 And 7the decoupling capacities 36 between the main ground plane 28 of the printed circuit board 8 and the portion 32 (supply voltage), and between the main ground plane 28 and the portion 33 (control voltage).

[0085] Access point 2 includes a motherboard 40 which contains radio frequency components. The main antenna 5 is connected to the motherboard via a coaxial cable 41 (50 Ω).

[0086] The first cable 34 and the second cable 35 are connected to the motherboard 8.

[0087] The motherboard 40 includes a power supply unit 42 and a processing unit 43.

[0088] The power supply unit 42 provides the supply voltage Vcc to the SPST switch 17 (via the first cable 34).

[0089] The processing unit 43 provides 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 radio frequency system (transition from the first radiation pattern to the second radiation pattern, and vice versa).

[0090] The processing unit 43 includes at least one processing component 43a, which is, for example, a "general-purpose" 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 Specific Integrated Circuit ).

[0091] The processing unit 43 further includes one or more memories 43b, connected to or integrated into 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 lead the processing component 43a to execute at least some of the steps of the following control process.

[0092] Processing unit 43: acquires a command to configure the radiation pattern of the radio frequency system 1 according to the first radiation pattern or the second radiation pattern; produces a control voltage Vc which depends on said command, and applies said control voltage to the input of the switching circuit (here on the fourth port 23 of the SPST switch 17.

[0093] We now describe an optimal position of the main antenna 5 and the radiation pattern matching device 6.

[0094] The main antenna 5 extends in a first plane P1, and the printed circuit board 8 extends in a second plane P2 perpendicular to the first plane P1.

[0095] The radiation pattern matching device 6 is therefore positioned perpendicularly above the main antenna 5.

[0096] A first distance d1 between the main antenna 5 and the printed circuit board 8, along a first axis X1 passing through the first plane P1 and perpendicular to the second plane P2, is equal to λ / 8.

[0097] A second distance d2 between the main antenna 5 and the printed circuit board 8, along a second axis X2 contained in the second plane and perpendicular to the second axis, is equal to λ / 16.

[0098] 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 at a chosen frequency (by calculating the free space wavelength with εr and µr equal to 1).

[0099] The main antenna 5 and the radiation pattern matching device 6 are connected to a common ground.

[0100] This common mass is also a mass of access point 2. It includes a metal grid 45 belonging to the chassis of access point 2.

[0101] For this purpose, the radio frequency system 1 includes a spring ground contact 46, which is fixed to the ground plane 28 of the printed circuit board 8 and to the metal grid 45.

[0102] We now describe the operating principle of the radio frequency system 1.

[0103] When the SPST switch 17 is in the open state (blocked mode), the current flow between the two radiating elements 10 is blocked and the radio frequency system 1 presents 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 board and the printed traces on it).

[0104] Indeed, even if the system is designed to minimize the surface area occupied and to ensure 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 slightly alters the shape of the initial diagram (this depends on the frequencies).

[0105] When the SPST switch 17 is in the closed state (passing mode) and the main antenna 5 emits 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 emitted by the main antenna 5.

[0106] We can then consider that the printed circuit board 8 and its components behave like a passive antenna which we will call a PR antenna for (Passive Reflecting antenna).

[0107] 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 according to its radiation pattern.

[0108] In this case, the electric field induces a voltage in the PR antenna between its radiating elements 10, and the magnetic field induces a surface current on the same radiating conductive parts. This voltage and current flowing through 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 predominantly in a predetermined direction. This phenomenon is entirely passive. The design of the PR antenna, with its reflector 25 printed on the printed circuit board 8, increases the directivity of the combined radiation, as the received waves are reflected.

[0109] We can 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.

[0110] The magnetic field is strongest in zones Z1 (greater than 1 A / m). The electric field is strongest in zones Z2 (greater than 300 V / m).

[0111] We can see that with the radiation pattern matching device 6 in forward mode, the gain of the radiation pattern increases in the direction of the negative side of the X-axis, and decreases in the other direction. Hole 47 is accentuated.

[0112] The radio frequency system 1 then presents a second radiation pattern having, compared to the first radiation pattern, an increased or decreased gain in at least one predetermined direction.

[0113] The efficiency of PR antenna reception 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.

[0114] In this configuration, the PR antenna essentially acts as a passive receiver and reflector that can capture a portion of the signal emitted and / or received by the main antenna. It does not amplify or improve the signal quality.

[0115] 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).

[0116] Reflection efficiency, energy losses, and electromagnetic interactions between antennas were taken into account to achieve the desired performance.

[0117] With reference to the figure 11 , the reflection rate ( return loss The main antenna 5 (C9 curve) has a low sensitivity (less than -10dB) over a wider bandwidth than the usable bandwidth 48 (operating frequency band). This allows us to anticipate a frequency shift due to its proximity to the PR antenna and avoid a decrease in its efficiency that could degrade its radiation performance and, consequently, the performance of access point 2 due to excessively high conducted reflection levels.

[0118] 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.

[0119] The transmission coefficient (C11 curve) between the two antennas, i.e. the coupling, must not be too strong so as not to impact the efficiency of the main antenna 5 too much and must not be too weak to create a real distinction between the two closed / open states of the SPST switch 17.

[0120] If the original signal is already too weak, the isolation created by the SPST 17 switch is of little use.

[0121] Advantageously, the transmission coefficient between the main antenna 5 and the radiation pattern matching device 6 is between -15 dB and -6 dB.

[0122] Table 1 (Appendix 1) illustrates an example of behavior obtained for a radio frequency system comprising a main antenna and the radiation pattern matching device.

[0123] The first column (from the left) corresponds to the initial 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 described previously.

[0124] The second column corresponds to the state of the SPST switch.

[0125] The third column gives the directivity values ​​for the three frequencies: 5180 MHz, 5500 MHz and 5800 MHz.

[0126] 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 %).

[0127] We can see on the figure 12 cross-sections of the radiation pattern (directivity) obtained along different planes; XZ, YZ and XY (the X, Y, Z axes are visible on the figure 5 ).

[0128] Table 2 (Appendix 2) is a table similar to Table 1, except that this time, in the first column, it is the inclination of the radiation pattern matching device 6 that varies.

[0129] We can see on the figure 13 cross-sections of the radiation diagram obtained along different planes; XZ, YZ and XY.

[0130] It has been indicated here that the switching circuit, i.e. the polarizing element of the receiving / reflecting device, is an SPST switch.

[0131] 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.

[0132] The switching circuit therefore does not necessarily include an SPST switch.

[0133] However, several of the possible alternatives have drawbacks that are difficult to overcome in the intended application because of the charged radio frequency environment, that is to say, due to 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.

[0134] The switching circuit could, for example, be a diode switching circuit.

[0135] With reference to the figure 14 The switching circuit 50 comprises a first capacitor 51 having one terminal connected to the radiating elements 10 and the reflector 25, a first inductor 52 having one terminal connected to the second terminal of the first capacitor 51 and a second terminal connected to ground. The cathode of 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 diode 53 is connected to the first terminal of the second capacitor 54. The second terminal of the second capacitor 54 is connected to the common ground of the equipment.

[0136] The circuit also includes 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 diode 53 and a second terminal connected to resistor 56.

[0137] 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.

[0138] Furthermore, it is difficult to control the bias voltage of diode 53 in a circuit very close to several antennas transmitting at a power exceeding 20 dBm. The risk with this type of circuit is that diode 53 will be permanently biased, and therefore either conducting or blocking, which negates the desired function.

[0139] We can see on the figure 15 The parameter curves S for the diode switching circuit 50: Sij (curve C12), Sji (curve C13), Sii (return loss port 1: curve C14), Sjj (return loss port 2: curve C15), in conducting mode. This can be seen on the figure 16 the same curves, in locked mode: curves C16, C17, C18, C19.

[0140] In addition to the constraints mentioned above related to the use of diodes, comparing the figures 8 , 9 And 15, 16 , it is clearly visible that the insertion losses are higher on the diode 50 circuit (almost 3 dB in the middle of the useful band, i.e. that almost 50% of the power of the signal passing through the circuit is lost) and the isolation is around 23 dB, which is not optimal compared to the SPST 17 switch whose insertion losses are at 0.7 max and the isolation is 10dB higher (34dB).

[0141] The SPST 17 switch is readily available commercially. Its characteristics are well-known and particularly relevant to this application. This component acts as a switch capable of allowing a radio frequency signal to pass through with low insertion loss or blocking it with an isolation of around 30dB in the 5 to 6GHz band. It can handle a maximum input power of 30dBm, which is more than sufficient.

[0142] We are now interested in, with reference to the figure 17 , to the mechanical integration of the radiation pattern adaptation device 6.

[0143] The main antenna 5 and the radiation pattern matching device 6 are mounted on the same support 60 made of plastic (in one piece).

[0144] The support 60 includes a first part 61 for receiving the main antenna and holding it in the position shown in the figures 3 à 5 .

[0145] The support 60 includes a second part 62 for accommodating the radiation pattern adaptation device.

[0146] The second part comprises a flat surface 63, generally rectangular in 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 extending perpendicularly to the flat surface 63 and from an edge thereof, and a second portion extending perpendicularly to the first portion and towards the interior of the flat surface 63.

[0147] The set of tabs includes, for the edge 64 (length of the flat surface) of the flat surface, a tab 65 located approximately at the center of said edge and of reduced length, and a tab 66 located near the edge 67 (width of the flat surface 63), also of reduced length. The set of tabs also includes a tab 68 which extends along the entire length of the edge 69 (width of the flat surface) and which continues along a portion of the length of the edge 70 (length of the flat surface) close to its midpoint.

[0148] A flexible finger 71, comprising a flat running portion, is defined in the thickness of the flat surface 63. The finger 71 has an end fixed to the flat surface 63 and a free end from which extends a hook 72 which protrudes perpendicularly to the flat surface 63 at the edge 67.

[0149] The radiation pattern matching device 6 is manually installed in the holder 60 as follows. The printed circuit board 8 is inserted into the holder 60 by pushing it in through the edge 67 of the flat surface 63 and pressing down on the hook 72. The printed circuit board 8 slides into the space formed between the flat surface 63 and the second portions of the tabs. When fully inserted, the hook 72 is no longer depressed and protrudes from the edge 75 of the printed circuit board 8, pressing against it and thus holding the printed circuit board 8 in place. The insertion of the printed circuit board 8 into the holder is therefore achieved via a sliding connection (created by the tabs), and its retention is achieved via an elastic snap-fit ​​(created by the flexible finger 71).

[0150] The radiation pattern matching device 6 can therefore be inserted into its holder and manually removed.

[0151] With reference to the figure 18 , the access point 2 comprises a plurality of radio frequency systems 1 as previously described, the main antennas 5 of said radio frequency systems being arranged to operate according to the MIMO technique.

[0152] Here, the access point has four radio frequency systems 1.

[0153] We can see that the support 60 mentioned earlier has an octagonal shape. It carries the four main antennas 5 and the four radiation pattern matching devices 6.

[0154] The plastic support 60 comprises four large faces 81 and four small faces 82 connecting said large faces 81.

[0155] Each radio frequency system 1, comprising a main antenna 5 and a radiation pattern matching device 6, is associated with a large separate face 81. For each large face 81, the support 60 is arranged so that the main antenna 5 extends outside the support 60, oriented at 45° and pressed against the outer 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 inner wall of said large face 81).

[0156] Table 3 in Annex 3 lists different cases, each corresponding to a distinct combination of radiation pattern matching device modes.

[0157] 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 blocked mode, and case 3 corresponds to a case where the matching devices are mounted and are all in passing mode.

[0158] Note that, for table 3, the NHPRP parameters ( Near Field Horizontal Partial Radiated Power ) at + / -45° and at + / -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 dθd 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 dθd Φ

[0159] We can see on the figure 19 For the frequencies 2437 MHz, 5500 MHz and 5800 MHz, the associated resulting radiation patterns are shown. For example, in case 3 at 5800 MHz, the increase in gain in the Y-axis direction (in both directions) is clearly visible.

[0160] Of course, the different embodiments are not limited to the embodiments and examples described but encompass all variants falling within the scope of the invention.

[0161] In other examples, the characteristics of the reflector are such that the reflector is suitable for controlling the radiation pattern of the main antenna for different center frequencies associated respectively with different operating bands, such as the operating bands included in the so-called "6 GHz" band of the Wi-Fi 6E protocol.

[0162] The reflector could have a different shape, for an even higher level of reflectivity.

[0163] It is also possible to enlarge the printed circuit board in order to add a series of reflectors (to obtain a Yagi antenna type antenna for example) in order to increase the natural directivity of the radiation pattern of the half-wave dipole.

[0164] The corners of the printed circuit board of the radiation pattern matching device are not necessarily cut out.

[0165] It has been described that the main antenna is positioned in a vertical plane and oriented to form a 45° angle 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 relative to the main antenna, which was described earlier, is a relative position with respect to the antenna's position and orientation.

[0166] All the numerical values ​​provided are given as examples. The frequency of the main antenna, for example, could be different from the frequencies listed here.

[0167] The radio frequency system can include any number of main antennas.

[0168] 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.

[0169] The radio frequency system can be integrated into any type of equipment that implements radio frequency communication. ANNEXES Appendix 1: Table 1

[0170] Table 1 is divided here into two tables: 1A, 1B (which form a single 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 1.7 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 1.8 -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 (thus, for the frequency 5180 MHz, the values ​​50.7 and 49.3 are associated with the row "+10 mm ON", the values ​​55 and 45 are associated with the row "+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 44.5 533 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 EP Eθ EP Eθ EP Tilt +30° ON 6 6.2 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 -30° tilt ON 6.5 6.7 6.4 1.6 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 49 595 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 adaptation device (6) comprising a printed circuit (8), on which two radiating strands (10) and a reflector (25) are printed, and on which a switching circuit (17) is mounted, connected to the two radiating strands and arranged to be controlled, such that: - when the switching circuit is located in a blocked mode, a current circulation between the two radiating strands (10) is blocked and the radiofrequency system (1) has a first radiation pattern; - when the switching circuit is located in a passing mode, the current circulation between the two radiating strands (10) is not blocked, such that the two radiating strands form a halfwave dipole antenna (18), the radiofrequency system (1) thus having a second radiation pattern having, with respect to the first radiation pattern, an increased or decreased gain in at least one predetermined direction; the radiofrequency system being characterized in that the main antenna (5) extends into a first plane (P1), and in that the printed circuit (8) of the radiation pattern adaptation device (6) extends into a second plane (P2) perpendicular to the first plane (P1).

2. Radiofrequency system according to claim 1, wherein 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 wherein 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.

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

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

5. Radiofrequency system according to claim 4, wherein the reflector (25) further comprises two secondary portions (27) which each extend from a distinct end of the main portion by being perpendicular to it.

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

7. Radiofrequency system according to claim 6, 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).

8. Radiofrequency system according to one of the preceding claims, wherein the switching circuit comprises a single pole single throw switch (17).

9. Radiofrequency system according to one of the preceding claims, further comprising a support (60) made of a single part 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 uninsert the radiation pattern adaptation device (6).

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

11. Radiofrequency system according to claim 10, the main antennas being arranged to operate according to the MIMO technique.

12. Piece of equipment comprising a radiofrequency system according to one of the preceding claims.

13. Piece of equipment according to claim 12, the equipment being an access point.

14. Control method, implemented by a processing unit (43) of a piece of equipment according to one of claims 12 or 13, and comprising the steps of: - acquiring a setpoint aiming 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 setpoint, and applying said control voltage at the input of the switching circuit.

15. Computer program comprising instructions which make a processing unit of the equipment according to one of claims 12 or 13 to execute the steps of the control method according to claim 14.

16. Computer-readable storage medium, on which the computer program according to claim 15 is stored.