Multi-beam receiving electronically steerable antenna

Abstract

A multi-beam receiving electronically steerable antenna (1) comprises: a Tx array (2, 6), the Tx array comprising a phased array of Tx antenna elements (3, 7) and having a geometric aperture with one or more pairs of parallel opposite sides; and an Rx array (2, 4), the Rx array comprising a phased array of Rx antenna elements (3, 5) and having a geometric aperture with one or more pairs of parallel opposite sides. The one or more pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are inclined relative to the one or more pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority benefit of Italian Patent Application No. 102019000024577 filed on December 18, 2019, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to an Electronically-Steerable Antenna (ESA), and in particular to a Multi-Beam on Receive (MBR) ESA. Background Art

[0004] Figure 1 A graphical representation of the operating principle of an MBR ESA compared to a conventional ESA is shown: In an MBR ESA, a smaller Tx antenna array illuminates a wide Field Of View (FOV) with a flood Tx illumination beam that can be electronically steered by real-time delay circuits (or more commonly phase shifters) within a defined Field Of Regard (FOR), while a larger Rx antenna array generates multiple narrow beam patterns pointing simultaneously in different directions from received signals entering antenna subarrays connected to associated receive and ADC chains, where the outputs of the antenna subarrays are digitally converted and processed to cover the entire angular sector of interest within the Tx illumination beam. For a general steering direction, the Rx antenna array generates multiple beams at different steering angles, which are skewed from each other by appropriate offsets that are generally proportional to the array beamwidth.

[0005] Figure 2a and Figure 2b An MBR ESA controller is shown, which includes a Tx section ( Figure 2a ), and includes an Rx section ( ) of a beamforming network designed to perform MBR processing and, in particular, enable the Rx array to receive multiple RF beams simultaneously Figure 2b ), the multiple RF beams are processed to simultaneously synthesize multiple Rx beams having Rx patterns with narrow Rx beamwidths, that is, the Rx beamwidths are each narrower than the Tx beamwidth.

[0006] Figure 3 Shown by Figure 2b The main beam pattern of multiple Rx beams simultaneously implemented by the digital beamformer in FIG. Figure 4The Tx pattern (light grey solid line) and the simultaneous multiple Rx patterns (dark grey solid lines) of the MBR ESA are shown, and Figure 5 Tx, Rx and bidirectional TRX (Tx-Rx) patterns associated with one skewed Rx beam are shown.

[0007] MBR ESAs may exhibit the same performance as conventional ESAs while reducing the probability of interception and supporting multiple functions to be performed simultaneously. However, in MBR ESAs, the sidelobe levels are larger than those in conventional ESAs due to the inevitable phase discontinuities on the slanted beams generated simultaneously at the receiving end when the number of digitized subarrays is not large enough.

[0008] Figure 6a , Figure 6b and Figure 6c The Rx patterns of simultaneous multiple Rx beams of MBR ESAs consisting of 8, 12, and 16 Rx digital channels are shown, respectively. As can be appreciated, when the number of digital Rx channels of the Rx array is limited, the increase in the number and level of side lobes becomes more problematic. In fact, consider the first side lobe of an MBR ESA consisting of 8 Rx digital channels as a reference ( Figure 6a ), using more Rx channels brings about 3dB SLL improvement in the case of 12 channels ( Figure 6b ) and brings about 7dB improvement in the case of 16 channels ( Figure 6c ).

[0009] Therefore, controlling the sidelobe level is a key issue in MBR ESA in order to guarantee the required performance. In fact, in MBR systems, when generating skewed simultaneous Rx beams, the sidelobe inevitably increases in level due to the phase discontinuity across the subarrays.

[0010] For example, the phase discontinuity model is Figure 7 , which depicts the equivalent time delay t (light grey solid line) of the nth Rx beam obtained from the sum of a single element (dashed line) and the qth subarray / Rx digital channel (dots), as well as the reference time delay (dark grey solid line) in the skew direction relative to the main direction (dashed line).

[0011] In the last few years, many solutions have been proposed to support designers in keeping the sidelobe level low (especially within a reference mask defined by the allowed sidelobe level guaranteeing the system performance) in mechanically / electronically steerable antennas, where most of the techniques are based on applying a non-uniform 2D illumination function to the radiated field. For example, in ESAs, the control of the illumination pattern is achieved by setting suitable values ​​for the variable attenuators of the TM / RM / TRM modules.

[0012] For example, a solution is proposed in US 5 781 157 A, which discloses a radar system comprising a transmitter, a receiver and a phased array antenna consisting of a plurality of subarrays. The transmitter is interconnected with certain laterally positioned subarrays of the antenna and other centrally arranged subarrays. The subarrays are interconnected to a multi-channel receiver via a beamformer, thereby providing a radar system with multiple beams with enhanced sidelobe suppression. Another form controls the transmit beam by applying a linearly varying phase function combined with a fixed increasing or decreasing phase function to the antenna array radiator.

[0013] Another solution is proposed, for example, in US 9 653 799 B2, which discloses a method of controlling the sidelobe distribution in an active electronically steerable antenna (AESA), comprising electronically reshaping the array aperture to reduce the sidelobes over a selected area of ​​the coverage volume of the array. In one example, the reshaping of the aperture is achieved by electronically turning on and / or off selected radiators in the array to change the angle of the edge discontinuity of the aperture and thereby move the main sidelobes out of the main plane(s) of operation of the array.

[0014] EP 2 613 169 A1 discloses a method for digitally distinguishing main lobe detection from grating lobe detection and side lobe detection without the need for additional antenna or receiver architecture. The method includes applying receive weights to return radar data for each radar receive element to steer each subarray of the array radar antenna to a direction other than the subarray transmit angle, and includes applying the subarray weights to each subarray to generate array radar antenna receive beam data having amplitude and phase components. The method includes applying a predetermined scale factor to the subarray beam data amplitude of each subarray to generate a scaled subarray beam data amplitude. The method includes generating guard beam data for each subarray based on the scaled subarray beam data amplitude. The method also includes determining whether the returned radar data corresponds to a main lobe, a grating lobe, or a side lobe based on the receive beam data and the guard beam data.

[0015] Ring Concentric Modular Antenna Array by KUZMIN ILYA A et al., 2019 IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EICONRUS), IEEE, 28 January 2019 (2019-01-28) Pages 2018-2019 addresses the need to reduce the large number of antenna elements of an active phased array antenna (APAA) while maintaining the directional scanning nature of APAA, and proposes to increase the distance between antenna elements by presenting a model of a modular circular antenna array comprising rectangular modules placed in several concentric circles, wherein the transmitters are grouped into row-column rectangular sub-arrays placed at angles to each other so as to reduce sidelobe levels and diffraction peaks while scanning.

[0016] BOAG AVIEL et al., Grating Lobe Mitigation in Ultra-wideband Phased Arrays, 2018, International Conference on Electromagnetics in Advanced Applications (ICEAA), IEEE, 10 September 2018 (2018-09-10), pp. 85-86 discloses an optimization technique for suppressing the number of grating lobes in ultra-wideband phased array antennas, wherein low computational complexity is achieved by effectively representing the array factor and observation direction over the desired frequency band and domain of the main beam. Subarray methods and fast array factor evaluation algorithms further reduce the computational cost.

[0017] ZAMANIFEKRI A et al., Beam Squint Compensation in Circularly Polarized Offset Reflector Antennas Using a Sequentially Rotated Focal-Plane Array, IEEE, Antennas and Wireless Propagation Letters, Vol. 14, 29 December 2014 (2014-12-29), pp. 815-818, addressed the problem of beam skew in circularly polarized offset reflector antennas and proposed the concept of using a focal plane array composed of sequentially rotated linear polarization elements and which can be used to facilitate beam steering in full-duplex communications with satellite internet (VSAT) operating in the Ka band. Summary of the invention

[0018] The object of the present invention is to provide an alternative solution to prior art sidelobe control solutions which allows a reduction in the number of digital Rx channels required to be acquired simultaneously while operating according to the MBR technique and which despite this reduction provides a significant reduction in the sidelobe level.

[0019] The present invention, as protected by the accompanying claims, relates to an MBR ESA and a method of reducing the sidelobe level in an MBR ESA. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The operating principle of an MBR ESA compared to a conventional ESA is schematically shown.

[0021] Figure 2a and Figure 2b Schematically shows a Tx segment ( Figure 2a ) and an Rx section including a beamforming network to perform MBR processing ( Figure 2b )'s MBR ESA controller.

[0022] Figure 3 Shown by Figure 2b The digital beamformer in the RF receiver implements the main beam pattern of multiple Rx beams simultaneously.

[0023] Figure 4 The Tx pattern of the MBR ESA and multiple Rx patterns simultaneously are shown.

[0024] Figure 5 Tx, Rx and bidirectional TRX patterns associated with one skewed Rx beam are shown.

[0025] Figure 6a , Figure 6b and Figure 6c The Rx patterns of simultaneous multiple Rx beams of the MBR ESA consisting of 8, 12, and 16 Rx digital channels are shown respectively.

[0026] Figure 7 A diagram plotting the phase shift discontinuities across the subarray is shown.

[0027] Figure 8a and Figure 8b An MBR ESA with a monostatic and a bistatic architecture is shown, respectively, and wherein the Tx array has a four-sided aperture that is rotated relative to the four-sided aperture of the Rx array.

[0028] Figure 9a and Figure 9b The 3D Tx patterns are shown when the Rx array is not rotated relative to the Rx array and when the Tx array is rotated at an angle of 45° relative to the Rx array, respectively.

[0029] Fig.10a and Fig.10b Bidirectional TRX patterns of MBR ESA steering with regular lattice and uniform illumination at 30° azimuth direction when the Tx array is not rotated relative to the Rx array and when the Tx array is rotated by an angle of 45° relative to the Rx array are shown, respectively.

[0030] Fig.10c Shows Fig.10a and Fig.10b Superposition of bidirectional TRX patterns shown in .

[0031] Fig.11 The bidirectional pattern of the MBR ESA (dark grey solid line) resulting from Rx pattern optimization for a skewed Rx beam (light grey solid line) is shown. DETAILED DESCRIPTION

[0032] The following description is provided to enable those skilled in the art to make and use the invention. Various modifications to the embodiments will be apparent to those skilled in the art without departing from the scope of the claimed invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein and defined in the appended claims.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed embodiments belong. In the event of a conflict, the present specification (including definitions) shall prevail. In addition, these examples are illustrative only and are not intended to be limiting.

[0034] To facilitate understanding of the embodiments described herein, reference will be made to certain embodiments, and specific language will be used to describe these embodiments. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present disclosure.

[0035] Consider the radar equation for the MBR ESA under the assumption that the disturbance is dominated by noise:

[0036]

[0037]

[0038] in:

[0039] SNR is the signal-to-noise ratio at the receiver's output;

[0040] P Avg is the average transmit power;

[0041] θ, is the steering angle

[0042] It is a bidirectional antenna pattern

[0043] G TX and G RX are Tx and Rx gains respectively,

[0044] G EL is the gain of each radiating element constituting the Tx array and the Rx array

[0045] D ARR is the directivity of a single array

[0046] L TAP is the cone loss due to uneven illumination

[0047] λ is the wavelength of the transmitted waveform

[0048] ToT is the target time (target exposure interval)

[0049] RCS is the target radar cross section

[0050] kToF is the density of the noise power

[0051] L RF is the loss caused by Tx and Rx paths

[0052] L PROC is process loss;

[0053] R is the distance from the sensor to the target.

[0054] The purpose of the present invention can be seen as how to optimize the bidirectional antenna pattern G 2-way (θ,Φ). Assuming that the Tx array and Rx array share the same antenna elements and uniform taper is applied in Tx, Equation 2 becomes:

[0055]

[0056] G EL depends on the chosen antenna element technology and G TX and G RX Depending on the number of radiating elements per array, the function to be optimized is the bidirectional TRX directivity function f 2 ' way (θ,Φ):

[0057]

[0058] According to one aspect of the present invention, the bidirectional TRX directivity function The optimization can be achieved by purposefully and appropriately differentiating the geometric apertures or shapes of the Tx array and the Rx array, in particular by introducing geometric aperture diversity between the Tx array and the Rx array that interrupts the geometric consistency between the geometric apertures of the Tx array and the Rx array to such an extent that the geometric apertures of the Tx array and the Rx array are geometrically uncorrelated, slightly correlated, or almost uncorrelated.

[0059] In particular, the geometric apertures of the Tx array and the Rx array are distinguished by rotating the geometric aperture of the Tx array relative to the geometric aperture of the Rx array (around the broadside direction orthogonal to the plane of the Tx array) while maintaining a common polarization direction between the Tx array and the Rx array.

[0060] Figure 8a and Figure 8b A simplification of the implementation of the invention is shown schematically in an MBR ESA, indicated as a whole by the reference numeral 1 .

[0061] exist Figure 8a and Figure 8b In the exemplary embodiment shown, the MBR ESA 1 is a single-base architecture ( Figure 8a ) (i.e., where the Tx array and the Rx array are collocated in the antenna plane) and with a bistatic architecture ( Figure 8b ) (i.e., where the Tx array and the Rx array are physically separated in the antenna plane) of a planar MBR ESA 1 (i.e., the Tx array and the Rx array are arranged in the antenna plane orthogonal to the broadside direction). In particular, in a single base station architecture ( Figure 8a), the MBR ESA 1 comprises a 2D Tx-Rx array 2 formed by a fully populated phased array of collocated transmit and receive antenna elements 3 that are individually selectable to transmit or receive RF signals, while in a dual-base architecture ( Figure 8b ), the MBR ESA 1 includes a 2D Rx array 4 formed by a fully-filled phased array of Rx antenna elements 5 only, and one or more 2D Tx arrays 6 that are physically separated from the Rx array and coplanar or parallel with it, and each of which is formed by a fully-filled phased array of Tx antenna elements 7 only.

[0062] The Tx-Rx array 2, Rx array 4 and (multiple) Tx arrays 6 are fully populated in the sense that the antenna elements 3, 5 and 7 are distributed in the respective arrays 2, 4 and 6 so as to satisfy the so-called half-wavelength spacing constraint, i.e. distributed in the antenna plane so as to be spaced approximately half a wavelength (λ / 2). The antenna elements 3, 5 and 7 may be fully excited (switched on) in the respective arrays 2, 4 and 6, or may be excited according to a suitable excitation pattern, such as an alternating or checkered pattern, in which the antenna elements are alternately switched on and off.

[0063] In both architectures, an antenna controller 8 is provided (see Figure 2a and Figure 2b ) so that the Tx antenna element transmits an RF beam having a scanning or non-scanning Tx pattern with a wide Tx beamwidth (flood beam), and so that the Rx antenna element receives simultaneous multiple RF beams, and these simultaneous multiple RF beams are processed to simultaneously synthesize multiple scanning or non-scanning Rx beams having an Rx higher gain pattern with a narrow Rx beamwidth, that is, the Rx beamwidths are each narrower than the Tx beamwidth.

[0064] In both architectures, the number of Tx antenna elements is lower than the number of Rx antenna elements, and the Tx beam has lower directivity than each Rx beam, so that the Tx beam has a wider azimuth and / or elevation beamwidth than each Rx beam.

[0065] exist Figure 8a and Figure 8b In the exemplarily shown embodiment, both the Tx antenna elements and the Rx antenna elements are arranged to form a corresponding 2D four-sided (or parallelogram-shaped or quadrilateral) geometric aperture having two pairs of parallel opposing (or facing) sides in the antenna plane.

[0066] The Tx antenna elements and the Rx antenna elements are evenly distributed in a dot matrix (or grid or grating) structure. Figure 8a and 8bIn the exemplary embodiment shown, the lattice is triangular, ie, the antenna elements are staggered between rows and columns. It goes without saying that the lattice structure may be different from a triangle, in particular may be rectangular, and the lattice structure may be equilateral or unequal.

[0067] In prior art solutions, each pair of parallel opposing sides of a four-sided aperture of the Tx array is parallel to a pair of parallel opposing sides of a four-sided aperture of the Rx array.

[0068] In the present invention, the four-sided aperture of the Tx array is rotated relative to the four-sided aperture of the Rx array to such an extent that each pair of parallel opposite sides of the four-sided aperture of the Tx array is tilted or inclined relative to the corresponding pair of parallel opposite sides of the four-sided aperture of the Rx array except for a non-zero angle α of 90°, in particular less than 90°.

[0069] In more detail, Figure 8a and Figure 8b In the embodiment exemplarily shown in FIG. , the Tx array has a square aperture, while the Rx array has a rectangular aperture.

[0070] In the above-mentioned prior art solutions, each pair of parallel opposing sides of the square aperture of the Tx array is parallel to the associated pair of parallel opposing sides of the rectangular aperture of the Rx array.

[0071] In the present invention, the square aperture of the Tx array is rotated 45° relative to the rectangular aperture of the Rx array, so that each pair of parallel opposite sides of the square aperture of the Tx array is inclined 45° relative to a pair of parallel opposite sides of the rectangular aperture of the Rx array.

[0072] Those skilled in the art, given the benefit of this disclosure, will appreciate that numerous other variations are possible in accordance with the principles disclosed herein.

[0073] In particular, in various embodiments, even a single pair of parallel opposing sides of the square aperture of the Tx array may be tilted relative to a pair of parallel opposing sides of the rectangular aperture of the Rx array, while other pairs of parallel opposing sides may be parallel.

[0074] For example, this may be the case where the Tx array has a square aperture and the Rx array has a parallelogram aperture whose short sides are tilted 45° relative to the long sides, and the square aperture of the Tx array is rotated 45° relative to the parallelogram aperture of the Rx array, so that a pair of parallel opposite sides of the square aperture of the Tx array are tilted 45° relative to a pair of longer sides of the parallelogram aperture of the Rx array, and another pair of parallel opposite sides of the square aperture of the Tx array are parallel to a pair of shorter sides of the parallelogram aperture of the Rx array.

[0075] Other examples may include four-sided apertures for the Tx array and the Rx array, such as non-right-angled rhombuses or rhombohedrons (equilateral trapezoids).

[0076] The applicants have experienced that benefits in terms of sidelobe level reduction similar to those allowed by a four-sided aperture of the Tx array and the Rx array can also be achieved by any polygonal aperture having one or more pairs of parallel opposing sides and wherein the geometric aperture diversity between the Tx array and the Rx array disrupts the geometric consistency between the geometric apertures of the Tx array and the Rx array to such an extent as to cause the geometric apertures of the Tx array and the Rx array to be geometrically uncorrelated or slightly correlated or barely correlated.

[0077] In the present invention, the high sidelobe levels along the main plane and originating from the parallelism between the parallel opposite edges of the associated pairs of geometric apertures of the Tx array and the Rx array are mitigated in the present invention: the near sidelobe levels are reduced, and since the zero degree angles of the Tx pattern are different from those of the Rx pattern, the mid and far sidelobes of the bidirectional TRX pattern are almost cancelled.

[0078] Figure 9a and Figure 9b 3D transmission pattern of a fully populated Tx array formed by 12×12 antenna elements and where the square aperture of the Tx array is not rotated relative to the rectangular aperture of the Rx array (α=0°) and correspondingly the square aperture of the Tx array is rotated relative to the rectangular aperture of the Rx array (α=45°)

[0079] Fig.10a and Fig.10b Bidirectional TRX patterns for MBR ESA steering with a regular lattice and where the square aperture of the Tx array is not rotated relative to the rectangular aperture of the Rx array (α=0°) and where the square aperture of the Tx array is rotated relative to the rectangular aperture of the Rx array (α=45°) respectively, at 30° azimuth direction (only one Rx beam is shown for clarity) for a fully populated Tx array with 12×12 antenna elements and an Rx array with 36×12 antenna elements ). Fig.10c Shows Fig.10a and Fig.10b Superposition of bidirectional TRX patterns shown in .

[0080] It can be understood that when the square aperture of the Tx array is rotated relative to the rectangular aperture of the Rx array ( Fig.10b , α=45°), and when the square aperture of the Tx array is not rotated relative to the rectangular aperture of the Rx array ( Fig.10a, α=0°), the mid-to-far sidelobe levels are significantly reduced compared to those with α=0°, while the benefit regarding the near sidelobe is limited because the first sidelobe of the Rx array is still located inside the main lobe of the Tx array.

[0081] In order to keep the near sidelobe level within a reference mask defined by the tolerated sidelobe level (which also guarantees system performance in MBR ESAs with a limited number of digital Rx channels), specific illumination functions can be applied to the attenuators and phase shifters of the Rx array. Outside the main lobe of the Tx array, the sidelobe level reduction achieved by rotating the geometrical aperture of the Tx array is already effective, so the optimization can conveniently be focused on a limited area only close to the main lobe.

[0082] Conventional weighted window-based techniques (such as Taylor weighting, Hamming weighting, Hanning weighting, Blackman-Harris window, etc.) should be abandoned because they lead to excessive tapering losses and result in further improvements in mid- and far-sidelobe levels (this is not strictly necessary in the case of rotating the Tx array relative to the Rx array).

[0083] According to another aspect of the present invention, the antenna controller 8 is also designed so that the optimized cone function is applied only to the near side lobes, i.e., with a stricter threshold for the near side lobes and a looser threshold for the far side lobes, without introducing excessive weighting losses. This optimization can be achieved by applying the optimized cone function only on the Rx pattern or the bidirectional pattern, taking into account all directions in azimuth and elevation where the side lobes are minimized.

[0084] Fig.11 The bidirectional pattern of the MBR ESA (dark grey solid line) resulting from Rx pattern optimization for a skewed Rx beam (light grey solid line) is shown. Fig.11 , the depicted Tx pattern (dashed line) originates from the pattern synthesis of the original Tx pattern (ie, the non-rotated pattern), and this results in relatively high mid-to-distal sidelobe levels.

[0085] In view of the preceding description, it can be appreciated the advantages that the present invention allows to achieve compared to prior art solutions.

[0086] In particular, the present invention can be applied to any MBR ESA and not only to conventional AESA without physical separation and size diversity between Tx array and Rx array, resulting in inclusion of monostatic and bistatic architectures.

[0087] Moreover, applying the present invention to an MBR ESA results in a significant reduction in mid- and far-side lobes due to the rotation of the Tx array relative to the broadside direction, and in a significant reduction in near-side lobes due to the application of optimized weighting coefficients, thereby ensuring improved system performance without using a larger number of Rx channels.

[0088] Furthermore, the present invention extends the geometric aperture diversity of the Tx array and the Rx array to any polygonal Tx pattern and Rx pattern, resulting in improved flexibility in utilizing the MBR ESA embodying the present invention.

Claims

1. A planar or quasi-planar multi-beam receiving electronically steerable antenna (1), comprising: A Tx array (2, 6) comprising a phased array of Tx antenna elements (3, 7) and having a geometric aperture with one or more pairs of parallel opposing sides in the Tx array plane; An Rx array (2, 4) comprising a phased array of Rx antenna elements (3, 5) and having a geometric aperture with one or more pairs of parallel opposing sides in an Rx array plane coplanar or parallel to the Tx array plane; The geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) so ​​that one or more pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are tilted or inclined at a non-zero angle other than 90° relative to one or more pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4); The multi-beam receiving electronically steerable antenna (1) further comprises an antenna controller (8), wherein the antenna controller (8) is designed to enable the Tx antenna element (3, 7) to transmit an RF Tx beam having a Tx pattern with a wide Tx beam width, and to enable the Rx antenna element (3, 5) to simultaneously receive a plurality of RF beams, wherein the plurality of RF beams can be processed to simultaneously synthesize a plurality of Rx beams having an Rx pattern with an Rx beam width each narrower than the Tx beam width; The number of the Tx antenna elements (3, 7) is lower than the number of the Rx antenna elements (3, 5); The Tx beam has lower directivity than each of the Rx beams, thereby causing the Tx beam to have a wider azimuth and / or elevation beamwidth than each of the Rx beams; and The Tx array (3, 7) has a lower gain than the Rx array (3, 5).

2. The multi-beam receiving electronically steerable antenna (1) according to claim 1, wherein: The geometric apertures of the Tx array and the Rx array (2, 4, 6) each include at least two pairs of parallel opposing sides; And wherein the geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) so ​​that two pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are inclined or tilted relative to the two pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4).

3. The multi-beam receiving electronically steerable antenna (1) according to claim 1, wherein: The geometric aperture of the Tx array and Rx array (2, 4, 6) is four-sided.

4. The multi-beam receiving electronically steerable antenna (1) according to claim 3, wherein: The geometric aperture of the Tx array (2, 6) is a square or a rhombus, and the geometric aperture of the Rx array (2, 4) is a rectangle or a parallelogram.

5. The multi-beam receiving electronically steerable antenna (1) according to claim 1, wherein the antenna controller (8) is further designed so that a cone function is applied only to the Rx pattern or to the Tx-Rx pattern, wherein one or more lower thresholds are associated with near side lobes and one or more higher thresholds are associated with mid and far side lobes.

6. The multi-beam receiving electronically steerable antenna according to claim 1, having a bistatic architecture, in which the Tx array and the Rx array (2, 4, 6) are physically separated, and the Tx array (6) is formed only by Tx antenna elements (7) and the Rx array (4) is formed only by Rx antenna elements (5).

7. The multi-beam receive electronically steerable antenna according to claim 1, having a monostatic architecture, in which the Tx array and the Rx array are juxtaposed to form a Tx-Rx array (2), wherein the antenna elements are both transmit and receive antenna elements (3) and are individually selectable to transmit or receive RF signals.

8. The multi-beam receiving electronically steerable antenna according to claim 1, wherein the antenna elements (3, 5, 7) are arranged in the corresponding Tx array and Rx array (2, 4, 6) so as to be spaced half a wavelength (λ / 2) so that the Tx array and Rx array (2, 4, 6) are completely filled.

9. A method for reducing the sidelobe level in a multi-beam receiving electronically steerable antenna (1), comprising: Providing a Tx array (2, 6) comprising a phased array of Tx antenna elements (3, 7) and having a geometric aperture with one or more pairs of parallel opposing sides in the Tx array plane; and Providing an Rx array (2, 4) comprising a fully populated phased array of Rx antenna elements (3, 5) and having a geometric aperture with one or more pairs of parallel opposing sides in an Rx array plane coplanar or parallel to the Tx array plane; wherein the geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) so ​​that one or more pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are tilted or inclined at a non-zero angle other than 90° relative to one or more pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4); The method further comprises: An antenna controller (8) is provided, wherein the antenna controller (8) is designed to cause the Tx antenna element (3, 7) to transmit an RF Tx beam having a Tx pattern with a wide Tx beamwidth, and to cause the Rx antenna element (3, 5) to simultaneously receive a plurality of RF beams, wherein the plurality of RF beams can be processed to simultaneously synthesize a plurality of Rx beams having Rx patterns with Rx beamwidths each narrower than the Tx beamwidth; in: The number of the Tx antenna elements (3, 7) is lower than the number of the Rx antenna elements (3, 5); The Tx beam has lower directivity than each of the Rx beams, thereby causing the Tx beam to have a wider azimuth and / or elevation beamwidth than each of the Rx beams; and The Tx array (3, 7) has a lower gain than the Rx array (3, 5).

10. The method according to claim 9, wherein: The geometric apertures of the Tx array and the Rx array (2, 4, 6) each include at least two pairs of parallel opposing sides; And wherein the geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) so ​​that two pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are inclined relative to the two pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4).

11. The method according to claim 9, wherein: The geometric aperture of the Tx array and Rx array (2, 4, 6) is four-sided.

12. The method according to claim 11, wherein: The geometric aperture of the Tx array (2, 6) is a square or a rhombus, and the geometric aperture of the Rx array (2, 4) is a rectangle or a parallelogram.

13. The method according to claim 9, wherein: The antenna controller (8) is also designed so that a cone function is applied only to the Rx pattern or to the Tx-Rx pattern, wherein one or more lower thresholds are associated with near side lobes and one or more higher thresholds are associated with mid and far side lobes.

14. The method according to claim 9, wherein: The multi-beam receiving electronically steerable antenna (1) is provided with a bistatic architecture in which the Tx array and the Rx array (2, 4, 6) are physically separated and the Tx array (6) is formed only by the Tx antenna elements (7) and the Rx array (4) is formed only by the Rx antenna elements (5).

15. The method according to claim 9, wherein: The multi-beam receiving electronically steerable antenna (1) has a monostatic architecture in which the Tx array and the Rx array are juxtaposed to form a Tx-Rx array (2), wherein the antenna elements are both transmitting and receiving antenna elements (3) and are individually selectable to transmit or receive RF signals.

16. The method according to claim 9, wherein: The antenna elements (3, 5, 7) are arranged in the respective Tx arrays and Rx arrays (2, 4, 6) so as to be spaced apart by half a wavelength (λ / 2) so that the Tx arrays and Rx arrays (2, 4, 6) are fully filled.

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