A beamforming doppler radar microstrip planar array antenna

Abstract

The application relates to a beamforming Doppler radar microstrip planar array antenna, which comprises a microstrip antenna layer, the microstrip antenna layer comprising a first microstrip series feed array group and a second microstrip series feed array group; the first microstrip series feed array group comprising a plurality of parallelly arranged first series feed arrays; the plurality of first series feed arrays having a first parallelogram shape; the first microstrip series feed array group comprising a plurality of parallelly arranged second series feed arrays; the plurality of second series feed arrays having a second parallelogram shape; the number of the first series feed arrays and the second series feed arrays being equal, and the first series feed arrays and the second series feed arrays being arranged at intervals; the first parallelogram and the second parallelogram being completely identical in shape and intersecting with each other, and the first parallelogram and the second parallelogram being symmetrical about the intersection line axis after intersection. The Doppler radar microstrip planar array antenna has better beamforming capability, the antenna main beam has gamma-psi separable characteristics, and the structural performance is more convenient to use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar, in particular to a beamforming Doppler radar microstrip planar array antenna. BACKGROUND

[0002] When the aircraft flies between the land and the sea surface, due to the difference in scattering characteristics of the sea surface and the land, the reflected energy has different frequency characteristics, which is manifested as the power spectrum shifting to the low frequency end in the Doppler response. This relative shift is usually called sea-land drift, which can cause significant speed measurement error of the Doppler radar system.

[0003] Currently, there are mainly two methods to overcome the influence of the above-mentioned sea-land drift. One method is to switch each beam of the antenna between two positions, but it needs to increase additional hardware devices, and the corresponding system processing time will also be prolonged; the other method is to perform "elliptical shaping" on the main beam 3dB profile of the array antenna to weaken the relative shift of the spectrum response corresponding to the land and the sea surface.

[0004] However, at present, there is a lack of array antenna with better shaping capability and convenient structure performance. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a beamforming Doppler radar microstrip planar array antenna to solve the problem of the existing Doppler radar beamforming.

[0006] The technical scheme provided by the present application is:

[0007] The present application discloses a beamforming Doppler radar microstrip planar array antenna, comprising a microstrip antenna layer, characterized in that the microstrip antenna layer comprises a first microstrip series feed line array group and a second microstrip series feed line array group.

[0008] The first microstrip series feed line array group comprises a plurality of first series feed line arrays arranged in parallel; the plurality of first series feed line arrays form a first parallelogram in shape.

[0009] The second microstrip series feed line array group comprises a plurality of second series feed line arrays arranged in parallel; the plurality of second series feed line arrays form a second parallelogram in shape.

[0010] The number of the first series feed line arrays and the second series feed line arrays is equal, and they are arranged at intervals; the first parallelogram and the second parallelogram are completely the same in shape and intersect with each other, and are symmetrical about the intersection axis after intersection.

[0011] Further, the microstrip antenna layer further comprises a first feed network and a second feed network respectively located on both sides of the first microstrip series feed line array group and the second microstrip series feed line array group.

[0012] The first feeding network and the second feeding network are connected with the first microstrip series-fed array group and the second microstrip series-fed array group at the same time;

[0013] The first feeding network provides a first feeding port and a second feeding port; the second feeding network provides a third feeding port and a fourth feeding port;

[0014] If feeding from the first feeding port, the fourth feeding port is a coupling port, and the second feeding port and the third feeding port are isolation ports;

[0015] If feeding from the second feeding port, the third feeding port is a coupling port, and the first feeding port and the fourth feeding port are isolation ports;

[0016] If feeding from the third feeding port, the second feeding port is a coupling port, and the first feeding port and the fourth feeding port are isolation ports

[0017] If feeding from the fourth feeding port, the first feeding port is a coupling port, and the second feeding port and the third feeding port are isolation ports.

[0018] Further, the first feeding network and the second feeding network both adopt a forward scanning mode, and the first microstrip series-fed array group and the second microstrip series-fed array group both adopt a backward scanning mode;

[0019] After feeding from the first, second, third or fourth feeding port respectively, a slanting directional beam A1 corresponding to the first feeding port, a slanting directional beam A2 corresponding to the second feeding port, a slanting directional beam A3 corresponding to the third feeding port, and a slanting directional beam A4 corresponding to the fourth feeding port are generated respectively.

[0020] Further, the slanting angle of the four beams is determined by setting the slanting angle of the first parallelogram and the second parallelogram.

[0021] Further, the first series-fed array and the second series-fed array both adopt a Doppler distribution, including a feeding line and a plurality of patches connected in series by the feeding line; the bending degree of the feeding line between the patches determines the phase difference between the patches;

[0022] The width of the patch is determined by the excitation amplitude loaded on the patch; and the length of the patch is determined by the working frequency of the microstrip planar array antenna.

[0023] Further, the first feeding network or the second feeding network both include a same number of four-port bridges connected in cascade as the number of the first series-fed array or the second series-fed array; the four-port bridges connect the first microstrip series-fed array group and the second microstrip series-fed array group together.

[0024] Further, the first feeding network or the second feeding network further comprises a plurality of double-branch transformation sections.

[0025] The double-branch transformation section is connected with a corresponding four-port bridge output port, and is used for adjusting the power division ratio of each output port, so that the feeding amplitude distribution in the first feeding network or the second feeding network is in a Taylor distribution.

[0026] Further, the four-port bridge is a'sun' shaped bridge, and the ports a-d of the'sun' shaped bridge are sequentially adjacent; in the first feeding network, the port c of an upper-stage'sun' shaped bridge is connected with the port a of a lower-stage'sun' shaped bridge, so as to form a cascade relationship of the bridges.

[0027] The port a of the first-stage'sun' shaped bridge is connected with the first feeding port; the port b of the i-th stage'sun' shaped bridge is connected with the i-th first string feed line array, and the port c is further connected with the i-th second string feed line array through a double transformation branch; the ports d of each stage'sun' shaped bridge are connected together through a double transformation branch, and are further connected with the second feeding port.

[0028] Further, the four-port bridge is a'sun' shaped bridge; the ports a-d of the'sun' shaped bridge are sequentially adjacent; in the second feeding network, the port c of an upper-stage'sun' shaped bridge is connected with the port a of a lower-stage'sun' shaped bridge, so as to form a cascade relationship of the bridges.

[0029] The port a of the first-stage'sun' shaped bridge is connected with the third feeding port; the port a of the i-th stage'sun' shaped bridge is connected with the i-th first string feed line array through a double transformation branch, and the port b is connected with the i-th second string feed line array; the ports d of each stage'sun' shaped bridge are connected together through a double transformation branch, and are further connected with the fourth feeding port.

[0030] Further, the size of the side length of the'sun' shaped structure of the'sun' shaped bridge meets the isolation degree requirement of the adjacent ports of the bridge.

[0031] The degree of inclination deformation of the'sun' shaped bridge meets the phase requirement of the beam pointing angle generated by the connection of the two end feed lines of the'sun' shaped bridge.

[0032] The present application can achieve at least the following beneficial effects:

[0033] The Doppler radar microstrip planar array antenna has better shaping capability, the antenna main beam has γ-ψ separable characteristics, and the structural performance is more convenient to use.

[0034] The technical solutions in the present application can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the following description, and some advantages will become apparent from the description, or will be understood by those skilled in the art through implementation of the present application. The purposes and other advantages of the present application can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated herein and constitute a part of the detailed description. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings:

[0036] Figure 1 A schematic diagram of a microstrip planar array antenna in an embodiment of the present application;

[0037] Figure 2 A schematic diagram of a microstrip antenna layer structure in an embodiment of the present application;

[0038] Figure 3 A schematic diagram of a simplified structure of a microstrip antenna layer in an embodiment of the present application;

[0039] Figure 4 A schematic diagram of a feed port configuration relationship in an embodiment of the present application;

[0040] Figure 5 A schematic diagram of a 3dB contour of a shaped pattern main lobe in an embodiment of the present application;

[0041] Figure 6 A schematic diagram of a beam configuration relationship in an embodiment of the present application;

[0042] Figure 7 A schematic diagram of an antenna coordinate system in an embodiment of the present application;

[0043] Figure 8 A schematic diagram of a "Ri" shaped electric bridge structure in an embodiment of the present application;

[0044] Figure 9 A schematic diagram of a "Ri" shaped electric bridge structure in an embodiment of the present application;

[0045] Figure 10 A top view of an upper surface of a radome in an embodiment of the present application.

[0046] REFERENCE NUMERALS:

[0047] 11 - mounting hole, 12 - shielding layer, 13 - radome, 14 - microstrip antenna layer, 15 - dielectric substrate, 16 - antenna supporting plate;

[0048] A - first microstrip series feed line array group, B - second microstrip series feed line array group, 1 - first feed network, 1' - second feed network, 2 - "day" shaped bridge structure, 3 - double transformation branch, 4 - feed line, 5 - patch. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present application will be described in detail with reference to the drawings, in which the same or similar components are denoted by the same reference numerals, and therefore the description will be omitted. The drawings constitute a part of this application, and are intended to explain the principles of the present application together with the embodiments of the present application, but are not intended to limit the scope of the present application.

[0050] One embodiment of the present application discloses a beamforming Doppler radar microstrip planar array antenna, as shown in the accompanying drawings, comprising a shielding layer 12, a radome 13, a microstrip antenna layer 14, a dielectric substrate 15 and an antenna backing plate 16. Figure 1 As shown in the accompanying drawings, the shielding layer 12 is located above the radome 13, the radome 13 is located above the microstrip antenna layer 14, the dielectric substrate 15 is located below the microstrip antenna layer 14, and the antenna backing plate 16 is located below the dielectric substrate 15.

[0051] Specifically, as shown in the accompanying drawings, the microstrip antenna layer 14 comprises a first microstrip series feed line array group and a second microstrip series feed line array group.

[0052] Specifically, as shown in the accompanying drawings, the microstrip antenna layer 14 comprises a first microstrip series feed line array group and a second microstrip series feed line array group. Figure 2 Or Figure 3 The first microstrip series feed line array group comprises a plurality of first series feed line arrays arranged in parallel; the plurality of first series feed line arrays form a first parallelogram shape in outline;

[0053] The second microstrip series feed line array group comprises a plurality of second series feed line arrays arranged in parallel; the plurality of second series feed line arrays form a second parallelogram shape in outline;

[0054] The first series feed line array and the second series feed line array have equal numbers of strips and are arranged at intervals; the first parallelogram shape and the second parallelogram shape are completely the same in shape and intersect with each other, and are symmetrical about the intersection axis after intersection.

[0055] As shown in the accompanying drawings, the first microstrip series feed line array group comprises 8 first series feed line arrays 1a-1h, and the second microstrip series feed line array group also comprises 8 second series feed line arrays.

[0056] As shown in the accompanying drawings, the first parallelogram shape in outline formed by the plurality of first series feed line arrays and the second parallelogram shape in outline formed by the plurality of second series feed line arrays are completely the same in shape and intersect with each other, and are symmetrical about the intersection axis after intersection. Figure 2 Figure 3 As shown in the accompanying drawings, the first microstrip series feed line array group comprises 8 first series feed line arrays 1a-1h, and the second microstrip series feed line array group also comprises 8 second series feed line arrays.

[0057] As shown in the accompanying drawings, the first parallelogram shape in outline formed by the plurality of first series feed line arrays and the second parallelogram shape in outline formed by the plurality of second series feed line arrays are completely the same in shape and intersect with each other, and are symmetrical about the intersection axis after intersection. Figure 4

[0058] ​​The microstrip antenna layer 14 further comprises a first feed network and a second feed network respectively located on both sides of the first microstrip series-fed array group and the second microstrip series-fed array group;

[0059] The first feed network and the second feed network are both connected to the first microstrip series-fed array group and the second microstrip series-fed array group;

[0060] The first feed network provides a first feed port and a second feed port; and the second feed network provides a third feed port and a fourth feed port;

[0061] If the first feed port is fed, the fourth feed port is a coupling port, and the second feed port and the third feed port are isolation ports;

[0062] If the second feed port is fed, the third feed port is a coupling port, and the first feed port and the fourth feed port are isolation ports;

[0063] If the third feed port is fed, the second feed port is a coupling port, and the first feed port and the fourth feed port are isolation ports;

[0064] If the fourth feed port is fed, the first feed port is a coupling port, and the second feed port and the third feed port are isolation ports.

[0065] More specifically, the first feed network and the second feed network both adopt a forward scanning mode, and the first microstrip series-fed array group and the second microstrip series-fed array group both adopt a backward scanning mode;

[0066] After being fed from the feed ports and being transmitted to the first microstrip series-fed array group and the second microstrip series-fed array group through the first feed network and the second feed network, the 3dB contour of the main beam of the antenna is approximately an ellipse in the γ-ψ coordinate system as shown in Figure 5 .

[0067] In the embodiment, the two microstrip series-fed array groups constituting the antenna are staggered, so that each beam can utilize the entire antenna aperture. The microstrip series-fed array group operates in a traveling wave state, and the amplitude distribution adopts a Doppler distribution, i.e., different end feeding can generate beams with opposite pointing angles.

[0068] As shown in Figure 6 , after being fed from the first, second, third or fourth feed port, respectively, a slanting pointing beam A1 corresponding to the first feed port, a slanting pointing beam A2 corresponding to the second feed port, a slanting pointing beam A3 corresponding to the third feed port, and a slanting pointing beam A4 corresponding to the fourth feed port are generated, respectively.

[0069] Preferably, the directions of the four slanting beams can be changed by changing the angles of the first and second parallelograms, i.e. the tilt angles of the first and second microstrip series-fed array groups.

[0070] As shown in Figure 7 , the tilt angle of the first and second microstrip series-fed array groups in the embodiment is the angle between the projection Y' of the beam pointing vector on the X-Y plane and the X axis, Y' is the projection of the beam pointing vector on the X-Y plane in the antenna aperture plane, γ is the angle between the beam axis and the X axis, ψ is the angle between the beam and the Z axis, the X axis is the heading of the aircraft, the Y axis is the direction transverse to the heading of the aircraft, and the Z axis is perpendicular to the plane in which the antenna is located. The tilt arrangement of the microstrip array antenna in the embodiment achieves separability of the aperture amplitude distribution function along the X-Y' axis, and makes the main beam of the antenna γ-ψ separable. The pattern produced by the amplitude A(x, y') = f(x)g'(y') distribution of the tilt can be γ-ζ separable, and the pattern function can be expressed as: F(γ, ζ) = s(γ)t'(ζ), where ζ is the angle between the beam pointing vector and the y' axis. Since ζ and ψ are reciprocal, the antenna pattern is approximately γ-ψ separable in the 3dB main lobe region, which is specifically manifested in that the 3dB contour of the main lobe of the antenna is approximately an ellipse in the γ-ψ coordinate system, and the major and minor axes are parallel to the coordinate axes (as shown in Figure 5 ). This “shaping” capability of the pattern separability is not possessed by conventional planar array antennas.

[0071] More specifically, the first and second series-fed arrays both adopt a Doppler distribution, and each includes a feed line and a plurality of patches connected in series by the feed line; the degree of bending of the feed line between the patches determines the phase difference between the patches;

[0072] The width of the patches is determined by the excitation amplitude loaded on the patches; and the length of the patches is determined by the operating frequency of the microstrip planar array antenna.

[0073] More specifically, the first or second feed network includes a same number of four-port bridges connected in cascade as the number of the first or second series-fed array; and the four-port bridges connect the first and second microstrip series-fed array groups together.

[0074] In addition, the first or second feed network further includes a plurality of double-stub transformation sections;

[0075] The double-stub transformation sections are connected to the output ports of the corresponding four-port bridges, and are used to adjust the power division ratio of each output port, so that the feed amplitude distribution in the first or second feed network is a Taylor distribution;

[0076] More specifically, the double branch conversion section includes a feed line and two patches connected in series through the feed line, the degree of bending of the feed line between the patches determines the phase difference between the patches; the width of the patches is determined by the excitation amplitude loaded on the patches; the length of the patches is determined by the operating frequency of the microstrip planar array antenna, and the output port power division ratio is set by setting the width of the two patches.

[0077] Preferably, the four-port bridge is a "sun" shaped bridge, and the ports a-d of the "sun" shaped bridge are sequentially adjacent.

[0078] In the first feeding network, the port c of the upper "sun" shaped bridge is connected with the port a of the lower "sun" shaped bridge, forming a cascade relationship of the bridges.

[0079] In the first feeding network, the port c of the upper "sun" shaped bridge is connected with the port a of the lower "sun" shaped bridge, forming a cascade relationship of the bridges.

[0080] In the first feeding network, the port c of the upper "sun" shaped bridge is connected with the port a of the lower "sun" shaped bridge, forming a cascade relationship of the bridges.

[0081] In the first feeding network, the port c of the upper "sun" shaped bridge is connected with the port a of the lower "sun" shaped bridge, forming a cascade relationship of the bridges.

[0082] More specifically, as shown in Figure 8 the four-port bridge is a "sun" shaped bridge, and the ports a-d of the "sun" shaped bridge are sequentially adjacent; the "sun" shaped bridge can realize feeding of the opposite ports, and by optimizing the side length of the "sun" shaped structure, the adjacent ports can maintain an isolation of above -25dB.

[0083] As shown in Figure 9 the "sun" shaped bridge is deformed by tilting, which can compress the space occupied by the "sun" shaped bridge structure, so that the phase difference between the ports b and c meets the beam pointing requirement. After being connected with the two end feed lines, the phase difference generated meets the phase requirement of the beam pointing angle.

[0084] Optionally, the microstrip planar array antenna further comprises a radome 13 above the microstrip antenna layer 14, a shielding layer 12 above the radome 13, a dielectric substrate 15 below the microstrip antenna layer 14, and an antenna base plate 16 below the dielectric substrate 15.

[0085] Optionally, the material of the antenna base plate 16 is aluminum, and the surface of the antenna base plate 16 is subjected to conductive oxidation treatment.

[0086] Optionally, the microstrip antenna layer 14 and the radome 13 are both processed from double-sided copper-clad dielectric board material, and the dielectric constant of the dielectric board material changes little with temperature and frequency, so as to facilitate the stability of the beam pointing angle.

[0087] Optionally, the thickness of the copper cladding is 0.035 mm.

[0088] Optionally, the dielectric board material is Rogers RT / duroid 6002.

[0089] Optionally, the thickness ratio of the dielectric substrate 15 to the radome 13 is 1:6, and the thickness of the antenna base plate 16 is 4 mm.

[0090] Optionally, the microstrip planar array antenna further comprises mounting holes 11, as shown in Figure 10 Optionally, the upper surface of the radome is etched with a shielding metal layer 12 or provided with a shielding metal layer 12 in the area corresponding to the feed network 1 and 1'. The mounting holes 11 are distributed around the radome 13, and the microstrip antenna layer 14 and the radome 13 are fixed to the antenna base plate 16 through the mounting holes 11.

[0091] Optionally, the overall size of the microstrip antenna layer 14 is 340 mm x 146 mm.

[0092] Compared with the prior art, the antenna provided by the embodiment has the following advantages:

[0093] 1. The microstrip array antenna of the embodiment realizes the separation of the aperture amplitude distribution function along the X-Y' axis: A(x, y') = f(x)g'(y'), Y' is the projection of the beam pointing vector on the X-Y plane of the antenna aperture, and the directional pattern generated by the "tilted" amplitude distribution is γ-ζ separable, and the directional pattern function can be expressed as: F(γ, ζ) = s(γ)t'(ζ), where ζ is the angle between the beam pointing vector and the y' axis. Since ζ and ψ are mutually exclusive, the antenna directional pattern is approximately γ-ψ separable in the 3dB main lobe region, which is specifically manifested in that the 3dB contour of the main lobe of the antenna is approximately an ellipse in the γ-ψ coordinate system, and the major and minor axes are parallel to the coordinate axes (as shown in Figure 5 ). The "shaping" capability of the directional pattern separability is not possessed by the traditional planar array antenna.

[0094] 2、The two groups of microstrip series feed array groups constituting the antenna are staggered arranged, so that each beam can utilize the whole antenna aperture. The microstrip series feed array groups work in the traveling wave state, and the amplitude distribution adopts Doppler distribution, i.e. feeding from different ends can produce beams with opposite pointing angles. The inclination angle of the linear array arrangement is the included angle between the projection Y' axis of the beam pointing vector in the X-Y plane and the X axis. This inclined arrangement mode makes the array amplitude distribution separable along the X-Y' axis, so that the antenna main beam has γ-ψ separable characteristic.

[0095] 3、The feed network is composed of cascaded H-shaped electric bridges. The H-shaped electric bridge can realize the feeding of opposite ports while maintaining more than -25dB isolation with adjacent ports. Meanwhile, the H-shaped electric bridge is tilted and deformed, so that the phase difference produced after connecting the H-shaped electric bridge with the two end feed lines exactly meets the phase requirement of the beam pointing angle. In addition, double branch transformation sections are adopted to adjust the power division ratio of each output port, so that the amplitude distribution of the array along the Y' axis is Taylor distribution.

[0096] 4、The microstrip antenna and the radome are designed in an integrated manner. The upper surface of the radome is partially covered with copper to shield the radiation of the feed network. Meanwhile, the dielectric loading of the radome can shorten the dielectric wavelength of the microstrip feed line and the size of the microstrip patch, so as to facilitate the array arrangement and meet the phase step between linear arrays. In addition, the integrated design of the antenna and the radome makes the influence of the radome on the beam pointing angle considered in the design, thereby improving the reliability of the antenna.

[0097] 5、The antenna has compact overall structure, low profile and easy processing advantages.

[0098] The above only describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A beamforming Doppler radar microstrip planar array antenna comprising a microstrip antenna layer, characterized in that, The microstrip antenna layer comprises a first microstrip string feed array group and a second microstrip string feed array group; The first microstrip string feed array group comprises a plurality of first string feed arrays arranged in parallel; the plurality of first string feed arrays have a first parallelogram shape; The second microstrip string feed array group comprises a plurality of second string feed arrays arranged in parallel; the plurality of second string feed arrays have a second parallelogram shape; The first string feed array and the second string feed array have the same number of strings and are arranged at intervals; the first parallelogram and the second parallelogram have the same shape and intersect with each other, and are symmetrical about the intersection line axis after intersection; The microstrip antenna layer further comprises a first feed network and a second feed network located on both sides of the first microstrip string feed array group and the second microstrip string feed array group, respectively; The first feed network and the second feed network are connected to the first microstrip string feed array group and the second microstrip string feed array group at the same time; The first feed network provides a first feed port and a second feed port; the second feed network provides a third feed port and a fourth feed port; If the first feed port is fed, the fourth feed port is a coupling port, and the second feed port and the third feed port are isolation ports; If the second feed port is fed, the third feed port is a coupling port, and the first feed port and the fourth feed port are isolation ports; If the third feed port is fed, the second feed port is a coupling port, and the first feed port and the fourth feed port are isolation ports If the fourth feed port is fed, the first feed port is a coupling port, and the second feed port and the third feed port are isolation ports; The first feed network or the second feed network comprises a plurality of four-port bridges connected in cascade, and the number of the four-port bridges is the same as the number of the first string feed array or the second string feed array; the four-port bridges connect the first microstrip string feed array group and the second microstrip string feed array group together; The first feed network or the second feed network further comprises a plurality of double-branch transformation sections; The double-branch transformation section is connected to the output port of the corresponding four-port bridge, and is used for adjusting the power distribution ratio of each output port, so that the feed amplitude distribution in the first feed network or the second feed network is a Taylor distribution; thereby making the amplitude distribution of the array along the Y' axis a Taylor distribution; the Y' axis is the projection of the beam pointing vector of the antenna in the X-Y plane of the antenna aperture; The double-branch transformation section comprises a feed line and two patches connected in series through the feed line, the bending degree of the feed line between the patches determines the phase difference between the patches; the width of the patch is determined by the excitation amplitude loaded on the patch; the length of the patch is determined by the working frequency of the microstrip planar array antenna, and the power distribution ratio of the corresponding output port is set by setting the width of the two patches; The first feed network and the second feed network adopt a forward scanning mode, and the first microstrip string feed array group and the second microstrip string feed array group adopt a backward scanning mode. After being fed from the first, second, third or fourth feed ports respectively, four beams are generated, respectively corresponding to the first feed port, the second feed port, the third feed port and the fourth feed port.

2. The Doppler radar microstrip planar array antenna according to claim 1, characterized in that The inclination angles of the four beams are determined by the inclination angles of the first parallelogram and the second parallelogram.

3. The Doppler radar microstrip planar array antenna according to any one of claims 1-2, characterized in that, The first and second string feed line arrays both adopt a Doppler distribution, and each includes a feed line and a plurality of patches connected in series by the feed line; the bending degree of the feed line between the patches determines the phase difference between the patches; The width of the patch is determined by the excitation amplitude loaded on the patch; and the length of the patch is determined by the working frequency of the microstrip planar array antenna.

4. The Doppler radar microstrip planar array antenna according to claim 3, characterized in that The four-port bridge is a "Ri" bridge, and the ports a-d of the "Ri" bridge are sequentially adjacent; in the first feed network, the port c of an upper "Ri" bridge is connected with the port a of a lower "Ri" bridge, thereby forming a cascade relationship of the bridges. The port a of the first "Ri" bridge is connected with the first feed port; the port b of the i-th "Ri" bridge is connected with the i-th first string feed line array, and the port c is further connected with the i-th second string feed line array through a double transformation branch; the ports d of each "Ri" bridge are connected together after passing through a double transformation branch, and then connected with the second feed port.

5. The Doppler radar microstrip planar array antenna according to claim 3, characterized in that The four-port bridge is a "Ri" bridge; the ports a-d of the "Ri" bridge are sequentially adjacent; in the second feed network, the port c of an upper "Ri" bridge is connected with the port a of a lower "Ri" bridge, thereby forming a cascade relationship of the bridges. The port a of the first "Ri" bridge is connected with the third feed port; the port a of the i-th "Ri" bridge is connected with the i-th first string feed line array through a double transformation branch, and the port b is connected with the i-th second string feed line array; the ports d of each "Ri" bridge are connected together after passing through a double transformation branch, and then connected with the fourth feed port.

6. The Doppler radar microstrip planar array antenna according to claim 4 or 5, characterized in that, The length of the "Ri" structure of the "Ri" bridge satisfies the isolation requirement of the adjacent ports of the bridge; The inclination deformation degree of the "Ri" bridge satisfies the phase requirement of the beam pointing angle generated after the two feed lines of the "Ri" bridge are connected.

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