Array antenna for millimeter wave automobile radar

Abstract

The invention relates to the technical field of antennas, in particular to an array antenna for a millimeter wave automobile radar, which comprises an antenna substrate, a feed layer, a reflecting layer and a radiation layer, the feed layer, the reflecting layer and the radiation layer are sequentially distributed in the antenna substrate from bottom to top, a placement groove is formed in the antenna substrate, and the radiation layer is arranged in the placement groove. Dielectric materials are filled between every two of the inner bottom of the antenna substrate, the feed layer, the reflecting layer and the radiation layer, through holes are formed in the surfaces of the dielectric materials, an array formed by four or more combined antenna rings is etched on the radiation layer, the combined antennas are distributed in a ring array mode, each combined antenna is composed of a grid unit and a patch unit, and the grid units and the patch units are arranged in a staggered mode. The grid units of the annular asymmetric radiation edges and the elliptical patch units are staggered to form the combined antenna, and then a dual-band multi-coupling mode is formed, so that different scene requirements are met, and the application universality of the antenna is improved.

Description

Technical Field

[0001] The invention relates to the technical field of antennas, in particular to an array antenna for millimeter wave automobile radar. Background Art

[0002] With the development of smart cars and driverless technology, automotive radar is becoming an increasingly important and indispensable part of cars. Millimeter-wave automotive radar array antenna is a multi-unit antenna system composed of regularly arranged radiating units (such as patches, slots, dipoles, etc.), which realizes beamforming and rapid scanning through phase or amplitude control, and is widely used in vehicle detection, ranging, speed measurement and imaging.

[0003] At present, in millimeter-wave automotive radars, multiple transmitting array antennas are required to achieve target detection and early warning at different ranges. Different detection distances will result in different antenna types required, and there are large differences in the scale of different antenna arrays, thereby meeting the needs of different gains and beams. In order to achieve the alternating start and stop function of multiple transmitting arrays, the front-end RF chip has to integrate multiple sets of parallel processing links. These links have significant time and space asynchronous characteristics in actual work, resulting in periodic idle waste of hardware resources. At the same time, the alternating work of antennas also increases the difficulty of front-end calculations.

[0004] In order to solve the above problems, the existing technology usually realizes the combination by connecting different antennas in series, so that the combined antenna forms multiple groups of resonances with different frequencies. However, due to the structural differences and functional requirements of the array antenna itself, the types of resonances are still fixed, which makes it difficult to meet the needs of different environments and situations when the car is used, which will limit the flexibility of the beam and thus cause limitations in automotive radar detection; Based on this, in order to solve the problem that when facing complex beam reception, the automobile radar array antenna is difficult to activate different resonances according to the on-site conditions in real time, and thus it is difficult to achieve dynamic perception, thereby affecting the accuracy of the automobile radar antenna, the present invention designs an array antenna for millimeter-wave automobile radar. Summary of the invention

[0005] The present invention provides an array antenna for millimeter-wave automotive radar, which solves the problem that when facing complex beam reception, the automotive radar array antenna is difficult to activate different resonances in real time according to the on-site conditions, and thus it is difficult to achieve dynamic perception, thereby affecting the accuracy of the automotive radar antenna. The present application forms a combined antenna by interlacing grid units with annular asymmetric radiation edges with elliptical patch units, thereby forming a dual-band multi-coupling mode, thereby meeting different scene requirements and improving the wide range of antenna use.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: An array antenna for a millimeter wave automobile radar comprises an antenna substrate, a feed layer, a reflective layer and a radiating layer, wherein the feed layer, the reflective layer and the radiating layer are sequentially distributed in the antenna substrate from bottom to top, an installation groove is provided in the antenna substrate, a dielectric material is filled between the bottom of the antenna substrate, the feed layer, the reflective layer and the radiating layer, a through hole is provided on the surface of the dielectric material, an array consisting of four or more combined antenna rings is etched in the radiating layer, the combined antenna is distributed in a circular array, the combined antenna is composed of a grid unit and a patch unit, the grid units are symmetrically distributed, the radiation side length of a single grid unit away from the midpoint of the combined antenna ring is greater than the radiation side length of the grid unit close to the midpoint of the combined antenna ring, and the antenna can be formed into a circular array as a whole by a double circular array, thereby forming a spatial filtering effect and improving the multipath interference suppression rate; the patch unit maintains linear polarization, the grid unit is regulated by non-uniform current distribution to achieve surface wave suppression, the patch unit provides a main radiation mode, and the combination of the two can achieve dual-band independent regulation, and the suppression ratio of rain and fog clutter is improved after the combined circular grid unit.

[0007] Preferably, the radiating edge is divided into an inner concave edge and an outer convex edge, the inner concave edge is a radiating edge of the grid unit away from the midpoint of the combined antenna ring, and the outer convex edge is a radiating edge of the grid unit close to the midpoint of the combined antenna ring, and a gradual impedance transition is formed through the coupling gap, thereby improving the reflection coefficient.

[0008] Preferably, the inner concave edge and the outer convex edge are both of asymptotic width, the width of the inner concave edge decreases from both ends to the center, and the width of the outer convex edge increases from both ends to the center. The inner concave edge forms a gradual equivalent inductance through width change to suppress high-frequency surface wave resonance, while the outer convex edge introduces distributed capacitance to compensate for the phase delay in the high-frequency segment.

[0009] Preferably, a unit connecting section is provided between the grid units, the patch unit is installed between the individual grid units and is elliptical, the patch unit is connected to the non-radiating edge of the grid unit through a microstrip line, the patch unit and the unit connecting section constitute a series patch antenna, and the series patch structure is utilized to make the unit connecting section and the elliptical patch form a cascade resonant cavity, and multi-beam radiation is generated by phase superposition, thereby realizing dynamic scene perception.

[0010] Preferably, a via is provided between the feeding layer and the radiation layer, and the via is located at the intersection of the non-radiating edge of the grid unit and the unit connection segment. The via is symmetrical about the midpoints of the multiple combined antenna rings, and the via is located at the intersection of the non-radiating edge of the grid unit and the unit connection segment. Symmetrical differential feeding is used to ensure that the currents of the grid radiation edges are in phase, thereby enhancing the radiation efficiency in the low frequency band.

[0011] Preferably, the area of ​​the middle region of the grid unit is smaller than that of the patch unit. The patch unit forms high-frequency resonant radiation, and the grid unit forms low-frequency resonant radiation. The grid unit with a smaller middle region covers the low frequency band through a low-order resonant mode, thereby being used for long-distance target detection; the patch unit occupies a larger area and covers the high frequency band through a high-order resonant mode, which is used for close-range wide-angle coverage. The two synergistically expand the total bandwidth of the dual-band and support the simultaneous processing of scene requirements at different distances.

[0012] Preferably, endpoint patches are provided at both ends of the patch unit, and the endpoint patches are trapezoidal. The trapezoidal endpoint patches form a positive resistance gradual transition zone through a gradual structure from the bottom wide side to the top narrow side.

[0013] Preferably, the feeding layer comprises a power division shifting structure, one end of the power division shifting structure is connected to the input strip line, and the other end of the power division shifting structure is connected to the radiation layer through a via hole.

[0014] Preferably, the unit connection section is divided into a radiation portion and an inclined portion, the inclination angle of the inclined portion is 12°, and a cutoff waveguide effect is formed at the edge of the radiation portion, thereby reducing surface wave attenuation.

[0015] The beneficial effects of the present invention are as follows: 1. The present invention proposes an array antenna for millimeter-wave automotive radar, which differentiates the wavelength width of the grid unit by changing the length of the radiation side of the grid unit. The long radiation side far away from the midpoint of the ring generates a wide beam through a low resonance frequency mode for wide-area short-range coverage; and the short radiation side close to the midpoint generates a narrow beam through a high-frequency resonance mode for long-distance high-precision detection; thereby realizing a dual-band mode to meet different scene requirements, and at the same time introducing a multi-mode coupling effect through an asymmetric structure, and the asymmetric layout of the long radiation side and the short radiation side of the adjacent unit destroys the periodic coupling path, thereby reducing interference with the main radiation mode.

[0016] 2. The present invention proposes an array antenna for millimeter-wave automotive radar, in which the inner concave edge forms wide-beam radiation by adjusting the radius of curvature, and is suitable for wide-area short-range coverage; the outer convex edge realizes narrow-beam high gain through a gradient gradual structure, and is used for long-distance target tracking. At the same time, the bandwidths of the two are matched, and a gradual impedance transition is formed through a coupling gap, thereby improving the reflection coefficient; at the same time, the asymmetric distribution of the inner concave edge and the outer convex edge destroys the periodic grating lobe, thereby optimizing the sidelobe level, and the asymmetric structure prolongs the fatigue life during vibration through a stress dispersion design.

[0017] 3. The present invention proposes an array antenna for millimeter-wave automotive radar, which forms a dual-band excitation mechanism through the combination of grid units and patch units. The low-frequency resonance mode is excited by the grid units with asymmetric radiation edge design, and the high-frequency resonance mode is generated by the difference in the current path of the elliptical patch units in the short axis direction, thereby realizing the combination of long-distance target coverage and close-range wide-angle coverage. At the same time, the high-frequency band reflection coefficient is optimized through the microstrip line connection with gradual impedance transformation; the series patch structure is used to make the unit connection segment and the elliptical patch form a cascade resonant cavity, and multi-beam radiation is generated by phase superposition, thereby realizing dynamic scene perception, activating different resonance modes in time-sharing, and shortening the switching time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation mode of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation mode or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are one implementation mode of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of each layer in the antenna substrate of the present invention; Figure 3 is a schematic diagram of a via hole of the present invention; Figure 4 yes Figure 3 The enlarged view of point A in the middle; Figure 5 is a top view of the present invention; Figure 6 is a schematic structural diagram of a single radiator of the present invention; Figure 7 It is a schematic diagram of the power distribution structure of the present invention; Figure 8 It is a schematic diagram of the unit connection section of the present invention; Fig. 9 yes Figure 8 Enlarged view of point B in the middle.

[0020] In the figure: 1. antenna substrate; 11. placement groove; 2. feeding layer; 21. power division shifting structure; 22. input strip line; 3. reflection layer; 4. radiation layer; 5. dielectric material; 51. through hole; 6. combined antenna; 7. grid unit; 71. radiation edge; 711. inner concave edge; 712. outer convex edge; 72. non-radiation edge; 73. unit connection section; 731. radiation part; 732. inclined part; 8. patch unit; 81. endpoint patch; 9. via. DETAILED DESCRIPTION

[0021] In order to better understand the above solution, the above technical solution is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] like Figure 1-2 As shown, an array antenna for millimeter wave automotive radar includes an antenna substrate 1, a feed layer 2, a reflective layer 3 and a radiation layer 4. The feed layer 2, the reflective layer 3 and the radiation layer 4 are sequentially distributed in the antenna substrate 1 from bottom to top. The antenna substrate 1 is provided with a placement groove 11. The antenna substrate 1 is a dielectric support base of a multi-layer structure, which can provide mechanical stability and an electromagnetic wave propagation environment. It also serves as a carrier of the feed layer 2, the reflective layer 3 and the radiating layer 4, thereby improving the integrity of the array antenna. The feed layer 2 realizes signal distribution and phase control through a stripline power division network, and is the core functional layer of beamforming. The reflective layer 3 serves as an all-metal floor, which enhances the forward radiation efficiency by reflecting electromagnetic wave energy, while suppressing backward leakage of electromagnetic waves. The radiating layer 4 is located on the surface, and is composed of a grid unit 7 and a patch unit 8 to form a radiator, which directly realizes electromagnetic wave radiation and multi-field coverage.

[0023] In the above layers, the signal flow transmission is reversely enhanced from the feeding layer 2 → the radiation layer 4 → the reflection layer 3; and the heat conduction path is the radiation layer 4 → the reflection layer 3 → the external heat sink, thus forming a complete array antenna.

[0024] The bottom of the antenna substrate 1, the feed layer 2, the reflective layer 3, and the radiation layer 4 are filled with dielectric material 5. Through holes 51 are provided on the surface of the dielectric material 5. The dielectric material 5 is used for electromagnetic performance regulation and thermal management. On the basis of bypassing the via hole 9, a hole with an aperture of 0.1-0.2 mm is provided on the dielectric material 5 to achieve heat dissipation. The aperture cannot be too large, otherwise it will cause electromagnetic leakage, and too small will lead to poor heat dissipation effect; under this aperture, the heat dissipation hole can also be used as an annular barrier hole to isolate the via hole 9, but on the one hand, compared with the traditional heat dissipation hole, its aspect ratio is less than 3:1, thereby ensuring the uniformity of copper plating on the hole wall, and at the same time, a high thermal conductivity and conductive coating is sprayed around the hole to compensate for the heat dissipation capacity after the aspect ratio is changed.

[0025] The radiation layer 4 is etched with an array consisting of four or more combined antennas 6 in a ring shape, and the combined antennas 6 are distributed in a ring array, and the combined antenna 6 is composed of a grid unit 7 and a patch unit 8; through the dual ring array method, the antenna as a whole can form a ring array, thereby forming a spatial filtering effect, and improving the multipath interference suppression rate. The patch unit 8 maintains linear polarization, and the grid unit 7 is regulated by non-uniform current distribution to achieve surface wave suppression. The patch unit 8 provides the main radiation mode. The combination of the two can achieve independent dual-band control. After combining the ring grid unit 7, the suppression ratio of rain and fog clutter is improved.

[0026] The grid units 7 are symmetrically distributed, and the length of the radiation side 71 of a single grid unit 7 away from the ring midpoint of the combined antenna 6 is greater than the length of the radiation side 71 of the grid unit 7 close to the ring midpoint of the combined antenna 6.

[0027] By changing the length of the radiation side of the grid unit 7, the wavelength width of the grid unit 7 is differentiated, and the long radiation side 71 away from the midpoint of the ring generates a wide beam through a low resonant frequency mode, which is used for wide-area short-range coverage (such as blind spot monitoring); The short radiating edge 71 near the midpoint generates a narrow beam through a high-frequency resonance mode for long-distance high-precision detection (such as adaptive cruise control); thereby realizing a dual-band mode to meet the needs of different scenarios. At the same time, a multi-mode coupling effect is introduced through an asymmetric structure. The asymmetric layout of the long radiating edge 71 and the short radiating edge 71 of the adjacent unit destroys the periodic coupling path, and the isolation between units is increased from about -18dB to about -25dB. The surface wave attenuation asymmetric edge current distribution increases the surface wave scattering loss, and the surface wave propagation efficiency is reduced by about 40%, thereby reducing interference with the main radiation mode. At the same time, the difficulty of etching is reduced, and the etching deviation can be tolerated through the setting of the long and short radiating edges 71.

[0028] like Figure 1-2 As shown, the radiation edge 71 is divided into an inner concave edge 711 and an outer convex edge 712. The inner concave edge 711 is the radiation edge 71 of the grid unit 7 away from the circular midpoint of the combined antenna 6, and the outer convex edge 712 is the radiation edge 71 of the grid unit 7 close to the circular midpoint of the combined antenna 6.

[0029] The inner concave edge 711 forms wide-beam radiation by adjusting the radius of curvature, which is suitable for wide-area short-range coverage; the outer convex edge 712 realizes narrow-beam high gain through a gradient structure, which is used for long-distance target tracking. At the same time, the bandwidths of the two are matched, and a gradual impedance transition is formed through the coupling gap, thereby improving the reflection coefficient; at the same time, the asymmetric distribution of the inner concave edge 711 and the outer convex edge 712 destroys the periodic grating lobe, thereby optimizing the sidelobe level, and the asymmetric structure prolongs the fatigue life during vibration through stress dispersion design.

[0030] like Figure 3-4 As shown, the inner concave edge 711 and the outer convex edge 712 are both of asymptotic width, the width of the inner concave edge 711 decreases from both ends to the center, and the width of the outer convex edge 712 increases from both ends to the center.

[0031] As the width of the inner concave edge 711 gradually decreases, a high impedance zone is formed in the central area, and a low impedance zone is formed in the edge area. A broadband matching is achieved through a gradual impedance transformation, thereby expanding the bandwidth. When the width of the outer convex edge 712 gradually increases, a capacitive load is formed at the radiation end to compensate for the high-frequency reactance component, thereby optimizing the reflection coefficient; the inner concave edge 711 induces high-density current aggregation at the smallest center width, and the outer convex edge 712 expands the current diffusion range at the largest end width. At the same time, the inner concave edge 711 forms a gradual equivalent inductance through width changes to suppress high-frequency surface wave resonance, while the outer convex edge 712 introduces distributed capacitance to compensate for the high-frequency phase delay.

[0032] like Figure 7-8 As shown, a unit connection section 73 is provided between the grid units 7, the patch unit 8 is installed between the individual grid units 7 and is elliptical, the patch unit 8 is connected to the non-radiating edge 72 of the grid unit 7 through a microstrip line, and the patch unit 8 and the unit connection section 73 constitute a series patch antenna.

[0033] The combination of the grid unit 7 and the patch unit 8 forms a dual-band excitation mechanism. The low-frequency resonance mode is excited by the grid unit 7 with an asymmetric radiation edge design, and the high-frequency resonance mode is generated by utilizing the difference in the current path in the short axis direction of the elliptical patch unit 8, thereby achieving a combination of long-distance target coverage and close-range wide-angle coverage. At the same time, the high-frequency band reflection coefficient is optimized through the microstrip line connection with gradual impedance transformation; the series patch structure is utilized to make the unit connection section 73 and the elliptical patch form a cascade resonant cavity, and multi-beam radiation is generated through phase superposition, thereby realizing dynamic scene perception, activating different resonance modes in time-sharing, and shortening the switching time.

[0034] like Figure 3-4 As shown, a via hole 9 is provided between the feed layer 2 and the radiation layer 4 , and the via hole 9 is located at the intersection of the non-radiating edge 72 of the grid unit 7 and the unit connecting section 73 , and the via hole 9 is symmetrical about the circular midpoint of the plurality of combined antennas 6 .

[0035] The via 9 is located at the intersection of the non-radiating edge 72 of the grid unit 7 and the unit connection section 73. The symmetrical differential feeding ensures that the currents of the grid radiation edge are in phase, thereby enhancing the radiation efficiency in the low frequency band. On the other hand, the currents of the non-radiating edge 72 are reversely offset, suppressing the propagation of surface waves and reducing the intensity of the near field. At the same time, the symmetrical layout forms a two-port balanced resonant cavity, which improves the isolation between the low-frequency mode of the grid unit 7 and the high-frequency mode of the patch unit 8, avoiding bandwidth compression caused by mode mixing.

[0036] Regarding the arrangement of vias 9 symmetrically arranged at the midpoint of the ring, the phase error between array units is reduced through equal path transmission delay design, and the symmetrical feeding network generates complementary current distribution, destroying the periodic grating lobe generation conditions, thereby optimizing the side lobes.

[0037] like Figure 5-6 As shown, the area of ​​the middle region of the grid unit 7 is smaller than that of the patch unit 8, the patch unit 8 forms high-frequency resonant radiation, and the grid unit 7 forms low-frequency resonant radiation. The grid unit 7 with a smaller middle region covers the low frequency band through a low-order resonant mode, so it is used for long-distance target detection. The small area design can suppress high-order mode interference. The patch unit 8 occupies a larger area and covers the high frequency band through a high-order resonant mode, which is used for close-range wide-angle coverage. The two work together to expand the total bandwidth of the dual-band and support the simultaneous processing of scene requirements at different distances; The area of ​​the middle region of the grid unit 7 is reduced, which reduces the edge coupling strength with the patch unit 8 and avoids the efficiency reduction caused by mode aliasing; The low-frequency current is concentrated at the edge of the grid unit 7, and the high-frequency current is distributed in the center of the patch, and the radiation efficiency is improved by impedance gradient matching; The grid unit 7 generates a high-gain narrow beam through a compact structure, which is used for long-distance vehicle tracking and high-frequency wide beam; while the patch unit 8 uses a wide area to form a wide-angle coverage beam, which is suitable for blind spot monitoring and close-range pedestrian detection.

[0038] like Figure 5 As shown, endpoint patches 81 are provided at both ends of the patch unit 8, and the endpoint patches 81 are trapezoidal; the trapezoidal endpoint patch 81 forms an impedance gradient transition zone through a gradient structure from the bottom wide side to the top narrow side. At the same time, the trapezoidal oblique edge destroys the parallel current distribution at the edge of the patch, reduces the attenuation of the surface wave, and the trapezoidal gradient structure realizes dual-band impedance overlap.

[0039] like Figure 6 As shown, the feeding layer 2 includes a power division shifting structure 21, one end of the power division shifting structure 21 is connected to the input strip line 22, and the other end of the power division shifting structure 21 is connected to the radiation layer 4 through a via 9. Impedance transformation is formed by gradual change of branch line width, and phase compensation is formed by using microstrip lines to compensate for high-frequency phase delay, thereby reducing the error between each radiating unit. A ring is used to replace the traditional tree-like power divider, shortening the total path length, reducing high-frequency insertion loss, and realizing multi-beam synchronous scanning. A plurality of groups of vias 9 are arranged with the center of the ring as the symmetry axis to suppress resonant cavity modal coupling.

[0040] like Figure 8As shown, the unit connecting section 73 is divided into a radiation portion 731 and an inclined portion 732. The inclined portion 732 has an inclination angle of 12°. The inclined portion 732 is provided to reduce the beam deflection amount through inclination compensation, thereby improving the main lobe gain. The 12° inclination angle changes the direction of the surface current, and forms a cutoff waveguide effect at the edge of the radiation portion 731, thereby reducing the surface wave attenuation. At the same time, the inclined portion 732 and the radiation portion 731 form a gradient heat conduction structure, thereby improving the heat dissipation effect.

[0041] A dual-frequency radiation structure is formed by the grid unit 7 and the patch unit 8, and differential feeding is formed by using symmetrical vias 9. At the same time, a ring-shaped power divider shifting structure 21 is used to transmit signals. When different external sudden situations occur, the emitted electromagnetic waves are dispersed to the grid unit 7 and the patch unit 8 when reflected to the radar antenna. The grid unit 7 and the patch unit 8 detect different waves and then differentially feed to the feed layer 2 through the via 9. The feed layer 2 forms signal transmission through the ring-shaped power divider shifting structure 21.

[0042] The basic principles and beneficial effects of the present invention are shown and described above. At the same time, the present invention is not limited to the above embodiments. Without departing from the effects and scope of the present invention, the present invention may have various changes and improvements. These changes and improvements all fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An array antenna for millimeter wave automotive radar, characterized in that: The invention comprises an antenna substrate (1), a feed layer (2), a reflective layer (3) and a radiating layer (4), wherein the feed layer (2), the reflective layer (3) and the radiating layer (4) are sequentially distributed in the antenna substrate (1) from bottom to top, a placement groove (11) is provided in the antenna substrate (1), a dielectric material (5) is filled between the bottom of the antenna substrate (1), the feed layer (2), the reflective layer (3) and the radiating layer (4), a through hole (51) is provided on the surface of the dielectric material (5), a combined antenna (6) is etched on the radiating layer (4), and four or more The above-mentioned combination antenna (6) is formed into a circular array and is etched on the upper surface of the radiation layer (4). The combination antenna (6) is distributed in a circular array. The combination antenna (6) is composed of grid units (7) and patch units (8). The grid units (7) are symmetrically distributed. The grid units (7) are divided into radiating edges (71) and non-radiating edges (72). The length of the radiating edge (71) of a single grid unit (7) away from the circular midpoint of the combination antenna (6) is greater than the length of the radiating edge (71) of the grid unit (7) close to the circular midpoint of the combination antenna (6).

2. The array antenna for millimeter wave automotive radar according to claim 1, characterized in that: The radiation edge (71) is divided into an inner concave edge (711) and an outer convex edge (712); the inner concave edge (711) is the radiation edge (71) of the grid unit (7) away from the circular midpoint of the combined antenna (6); and the outer convex edge (712) is the radiation edge (71) of the grid unit (7) close to the circular midpoint of the combined antenna (6).

3. The array antenna for millimeter wave automotive radar according to claim 2, characterized in that: The inner concave edge (711) and the outer convex edge (712) are both of asymptotic width, the width of the inner concave edge (711) decreases from both ends to the center, and the width of the outer convex edge (712) increases from both ends to the center.

4. The array antenna for millimeter wave automotive radar according to claim 2, characterized in that: A unit connection section (73) is provided between the grid units (7); the patch unit (8) is installed between the individual grid units (7) and is elliptical; the patch unit (8) is connected to a non-radiating edge (72) via a microstrip line; and the patch unit (8) and the unit connection section (73) form a series patch antenna.

5. The array antenna for millimeter wave automotive radar according to claim 4, characterized in that: A via hole (9) is provided between the feed layer (2) and the radiation layer (4), the via hole (9) is located at the intersection of the non-radiation edge (72) and the unit connection section (73), and the via hole (9) is symmetrical about the circular midpoint of the plurality of combined antennas (6).

6. The array antenna for millimeter wave automotive radar according to claim 4, characterized in that: The area of ​​the middle region of the grid unit (7) is smaller than the area of ​​the patch unit (8); the patch unit (8) forms high-frequency resonant radiation, and the grid unit (7) forms low-frequency resonant radiation.

7. The array antenna for millimeter wave automotive radar according to claim 6, characterized in that: End point patches (81) are provided at both ends of the patch unit (8), and the end point patches (81) are trapezoidal.

8. The array antenna for millimeter wave automotive radar according to claim 5, characterized in that: The feed layer (2) comprises a power division shifting structure (21), one end of the power division shifting structure (21) is connected to an input strip line (22) installed on the feed layer (2), and the other end of the power division shifting structure (21) is connected to the radiation layer (4) through a via (9).

9. The array antenna for millimeter wave automotive radar according to claim 4, characterized in that: The unit connection section (73) is divided into a radiation portion (731) and an inclined portion (732), and the inclined portion (732) has an inclination angle of 12°.

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