Sparse array antenna with normal beam inclination

Abstract

The invention provides a sparse array antenna with a tilted normal beam, which comprises waveguide antenna units, a plurality of waveguide antenna units adopt the same open waveguide antenna structure, each waveguide antenna unit comprises a first metal cavity and a second metal cavity which are communicated, one end of the first metal cavity is arranged on a working plane and receives a radio frequency signal, and the other end of the first metal cavity is arranged on the working plane. The first metal cavity and the second metal cavity which are communicated form a radio frequency signal propagation path; a radiation port of the waveguide antenna unit is arranged at one end, far away from the first metal cavity, of the second metal cavity; a first inclined included angle is formed between the plane where the radiation port is located and the working plane, so that the antenna pattern of the waveguide antenna unit performs normal offset at the first inclined included angle; wherein the plurality of waveguide antenna units are arranged according to a sparse array. The normal beam inclined phased array sparse array open waveguide antenna provided by the invention has the advantages of low profile, low cost, high integration and phase scanning, and has high application value.

Description

Technical Field

[0001] The present invention relates to the technical field of phased array antennas, and in particular to a sparse array antenna with a tilted normal beam. Background Art

[0002] In wireless communication systems, antenna performance plays a vital role in communication quality. Traditional antennas are usually installed vertically or horizontally. In certain scenarios, this installation method may not meet the signal coverage and reception requirements. In this case, it is necessary to adjust the radiation direction and coverage area of ​​the signal by adjusting the direction of the antenna beam, so that the signal is more concentrated in a specific target area, reducing unnecessary coverage waste and improving the effective utilization of the signal.

[0003] At present, the technical solution to achieve the normal tilt of the antenna generally adopts the method of adding additional structural parts to achieve the tilt of the normal beam through the physical offset of the antenna. Figure 1 The figure shows a traditional antenna tilt model, which raises one end of the phased array antenna as a whole to achieve the purpose of tilting the normal beam of the antenna. However, this will increase the overall weight of the antenna and the antenna design cost. In addition, raising the antenna as a whole will increase the thickness of the antenna (the height difference between the two sides of the antenna), making it difficult to achieve the purpose of miniaturization and compact structural design.

[0004] In addition, in phased array antennas, the increase in the number of array elements will lead to the increasing complexity of the power division and feeding network, resulting in a significant increase in system costs. In order to solve the above problems, sparse array antennas are often selected in the array unit arrangement design. The characteristic of sparse array antennas is that when the antenna aperture size does not change, the number of array elements is reduced to a certain extent and a new array antenna is formed, and its main beam width does not change significantly. The antenna still has good directivity, and the system cost and complexity are reduced by reducing the number of antenna units; and by optimizing the position of the array elements, a sidelobe level better than the full array can be obtained. However, at present, sparse array antennas are basically used in planar arrays, and there is no precedent for their application in tilted arrays. In other words, there is no case proposing the combination of tilted arrays and sparse arrays, and there is also a lack of specific implementation methods for effectively combining tilted arrays and sparse arrays. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art.

[0006] To this end, the present invention provides a sparse array antenna with tilted normal beam.

[0007] The present invention provides a sparse array antenna with a normal beam tilt, comprising:

[0008] A waveguide antenna unit, wherein the plurality of waveguide antenna units adopt the same open waveguide antenna structure, wherein the waveguide antenna unit comprises a first metal cavity and a second metal cavity that are connected, wherein one end of the first metal cavity is arranged on a working plane and receives a radio frequency signal, and the first metal cavity and the second metal cavity that are connected form a propagation path of the radio frequency signal;

[0009] The radiation port of the waveguide antenna unit is arranged at one end of the second metal cavity away from the first metal cavity; the plane where the radiation port is located forms a first tilt angle with the working plane, so that the antenna pattern of the waveguide antenna unit is normally offset at the first tilt angle;

[0010] Among them, several waveguide antenna units are arranged in a sparse array.

[0011] The sparse array antenna with normal beam tilt according to the above technical solution of the present invention may also have the following additional technical features:

[0012] In the above technical solution, the ends of the first metal cavities of the plurality of waveguide antenna units are arranged on the same working plane;

[0013] The heights of the plurality of waveguide antenna units are equal.

[0014] In the above technical solution, the method of arranging a plurality of waveguide antenna units in a sparse array includes:

[0015] Arranging a plurality of waveguide antenna units in a planar sparse array manner to obtain a planar sparse array layout diagram; wherein the planar sparse array uses the working plane as a reference plane;

[0016] Mapping the position of each array element in the planar sparse array layout diagram to the inclined plane one by one to obtain an inclined sparse array layout diagram, wherein the position of the array element is the position where the waveguide antenna unit is placed, and the inclined plane is a plane inclined at a first inclined angle to the reference plane;

[0017] Arrange a plurality of the waveguide antenna units according to a tilted sparse array layout diagram.

[0018] In the above technical solution, the density of array elements in the inclined sparse array layout diagram is greater than the density of array elements in the planar sparse array layout diagram.

[0019] In the above technical solution, the method of arranging the plurality of waveguide antenna units in a sparse array also includes:

[0020] The antenna array formed after being arranged according to the tilted sparse array layout diagram is simulated to optimize and adjust the position of each array element.

[0021] In the above technical solution, one end of the first metal cavity close to the second metal cavity has an inclined assembly surface, and the inclined assembly surface forms a first inclined angle with the working plane. The second metal cavity is assembled on the inclined assembly surface so that the plane where the radiation port is located forms a first inclined angle with the working plane.

[0022] In the above technical solution, the first metal cavity includes a straight waveguide section and an inclined waveguide section, one end of the straight waveguide section is arranged on a working plane to receive a radio frequency signal, and the arrangement direction of the straight waveguide section is perpendicular to the working plane, the inclined waveguide section is connected to the other end of the straight waveguide section, and the arrangement direction of the inclined waveguide section forms a first inclined angle with the arrangement direction of the straight waveguide section, and the inclined waveguide section is connected to the second metal cavity.

[0023] In the above technical solution, the second metal cavity adopts an impedance gradient structure;

[0024] And, the aperture of the second metal cavity is larger than that of the first metal cavity.

[0025] In the above technical solution, the waveguide antenna unit adopts an air waveguide form, a ridge waveguide form, or a dielectric-filled waveguide form.

[0026] In the above technical solution, the first inclination angle is greater than 0 degree and less than or equal to 20 degrees.

[0027] In summary, due to the adoption of the above technical features, the beneficial effects of the present invention are:

[0028] The present invention proposes a low-profile, low-cost, highly integrated, phase-scannable normal beam tilted phased array sparse array open waveguide antenna, which has high application value. Specifically, in the normal beam tilted sparse array antenna proposed in the present invention, a waveguide antenna unit with a tilted radiation aperture is first designed, and then the unit antennas are arranged into an array by a sparse array projection method. Without adding additional tilted structural parts, the normal offset of the phased array antenna can be achieved. Compared with the traditional physical offset, the antenna profile height is reduced, the antenna weight is reduced, the antenna design cost is saved, and the antenna miniaturization design is achieved. At the same time, the normal tilted sparse phased array antenna proposed in the present invention has good directivity and scanning capability. By optimizing the distribution of antenna array elements, a sidelobe level lower than the full array can be obtained, and after the array is sparse, a part of the antenna units are reduced compared to the full array, thereby simplifying the entire feeding network and the overall structure, and reducing the complexity of the system.

[0029] Additional aspects and advantages of the present invention will become apparent from the following description or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0031] Figure 1 It is a schematic diagram of the traditional antenna tilt model;

[0032] Figure 2 It is a schematic structural diagram of a waveguide antenna unit in a sparse array antenna with normal beam tilt according to an embodiment of the present invention;

[0033] Figure 3 yes Figure 2 Schematic diagram of the simulation results of S11 (input reflection coefficient) of the waveguide antenna unit shown;

[0034] Figure 4 yes Figure 2 A schematic diagram comparing antenna radiation patterns of the waveguide antenna unit shown and a conventional planar waveguide antenna unit;

[0035] Figure 5 is a planar sparse array layout diagram provided in one embodiment of the present invention;

[0036] Figure 6 In one embodiment of the present invention, Figure 5 Schematic diagram of the planar waveguide sparse array antenna structure formed on the basis;

[0037] Figure 7 yes Figure 6 The antenna scanning pattern of the planar sparse array shown (frequency 92GHz);

[0038] Figure 8 It is a schematic diagram of the principle of mapping relationship from a planar sparse array to an inclined sparse array in one embodiment of the present invention;

[0039] Fig. 9 is a diagram of a tilted sparse array layout provided in one embodiment of the present invention;

[0040] Fig.10 is a schematic diagram of the structure of a tilted waveguide sparse array antenna in one embodiment of the present invention;

[0041] Fig.11 yes Fig.10 The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 92GHz);

[0042] Fig.12 yes Fig.10 The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 93GHz);

[0043] Fig.13 yes Fig.10The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 94GHz);

[0044] Fig.14 is a side view of a sparse array antenna with normal beam tilt according to an embodiment of the present invention;

[0045] Fig.15 is a schematic structural diagram of a waveguide antenna unit in a sparse array antenna with normal beam tilt according to another embodiment of the present invention;

[0046] Fig.16 is based on Fig.15 A schematic diagram of a sparse array antenna structure formed by waveguide antenna units is provided;

[0047] Fig.17 yes Fig.16 The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 92GHz);

[0048] Fig.18 yes Fig.16 The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 93GHz);

[0049] Fig.19 yes Fig.16 The antenna scanning pattern of the tilted waveguide sparse array antenna shown (frequency 94GHz);

[0050] Fig. 20 is a schematic structural diagram of a waveguide antenna unit in the form of a ridge waveguide in one embodiment of the present invention;

[0051] Fig.21 It is a schematic structural diagram of a waveguide antenna unit in the form of a dielectric-filled waveguide in one embodiment of the present invention.

[0052] in, Figures 1 to 21 The corresponding relationship between the reference numerals and the component names is as follows:

[0053] 1. First metal cavity; 2. Second metal cavity;

[0054] 11. Inclined assembly surface; 12. Straight waveguide section; 13. Inclined waveguide section. DETAILED DESCRIPTION

[0055] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0056] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0057] Refer to the following Figures 1 to 21 The sparse array antenna with normal beam tilt provided according to some embodiments of the present invention is described.

[0058] Some embodiments of the present application provide a sparse array antenna with a tilted normal beam.

[0059] The first embodiment of the present invention provides a sparse array antenna with tilted normal beam, comprising a plurality of waveguide antenna units.

[0060] Several waveguide antenna units adopt the same open waveguide antenna structure, and the waveguide antenna unit includes a first metal cavity and a second metal cavity that are connected, one end of the first metal cavity is arranged on a working plane and receives a radio frequency signal, and the connected first metal cavity and the second metal cavity form a propagation path of the radio frequency signal; the radiation port of the waveguide antenna unit is arranged at one end of the second metal cavity away from the first metal cavity; the plane where the radiation port is located is at a first tilt angle with the working plane, so that the antenna pattern of the waveguide antenna unit is normally offset at the first tilt angle; wherein, several waveguide antenna units are arranged in a sparse array. The first tilt angle is the target angle for the antenna pattern offset, and its value is greater than 0 and less than or equal to 20°. In the present disclosure, the maximum value of the first tilt angle of 20° is used as an example for schematic description.

[0061] It should be noted that in the field of millimeter wave antenna technology, metal open waveguides (i.e., open waveguide antenna structures) are relatively common phased array antenna array units, which have the advantages of simple structure, large radiation power capacity, and low loss, and are widely used in many antennas. Metal open waveguides can be used as two-dimensional scanning phased array antenna units to achieve two-dimensional phase scanning of array antennas; while general microstrip antennas are difficult to use in tilted arrays due to the limitations of high-frequency patch size and high loss of microstrip feed networks at high frequencies.

[0062] Figure 2A schematic diagram of the structure of the waveguide antenna unit in some embodiments is shown. The present disclosure takes the working frequency band of the waveguide antenna unit as 92 GHz to 94 GHz and the transmission of W-band radio frequency signals as an example for explanation. The outer layer of the waveguide antenna unit is a metal cavity, and there is no filling medium inside, that is, an air waveguide form is adopted. Specifically, the metal cavity is divided into a first metal cavity 1 and a second metal cavity 2. The first metal cavity 1 has an inclined assembly surface 11 at one end close to the second metal cavity 2. The inclined assembly surface 11 is at a first inclined angle with the working plane. The second metal cavity 2 is assembled on the inclined assembly surface 11 so that the plane where the radiation port is located is at a first inclined angle with the working plane. In general, the second metal cavity 2 adopts an impedance gradient structure; and the aperture of the second metal cavity 2 is larger than the aperture of the first metal cavity 1, which is used to achieve impedance matching. The S11 simulation result of the waveguide antenna unit obtained after optimizing the port standing wave is as shown in the figure. Figure 3 shown. Figure 4 A comparison diagram of the directional pattern of the waveguide antenna unit disclosed in the present invention and the directional pattern of a conventional planar waveguide antenna unit is shown. It can be seen that the directional pattern of the waveguide antenna unit disclosed in the present invention is offset by 20° in the normal direction compared with the directional pattern of the conventional planar waveguide antenna unit.

[0063] Based on the above waveguide antenna unit, the ends of the first metal cavities of several waveguide antenna units can be arranged on the same working plane in the phased array antenna; the heights of several waveguide antenna units are equal. In this way, the antenna cross-section height can be reduced and the normal offset of the phased array antenna can be achieved.

[0064] In the present disclosure, the antenna array is arranged in a sparse array to optimize the performance of the tilted array antenna. It should be noted that arranging the tilted array antenna in a sparse array is not something that a person skilled in the art can easily think of based on needs. On the one hand, for traditional tilted array antennas, due to their structural limitations, it is difficult to achieve a sparse array arrangement based on overall tilt. On the other hand, the traditional tilted array antenna will have a greater impact on the side lobes and gain after being arranged in a sparse array.

[0065] The waveguide antenna unit proposed in the present disclosure makes it possible to arrange the tilted array antenna in a sparse array.

[0066] In some embodiments, the manner in which the plurality of waveguide antenna units are arranged in a sparse array includes:

[0067] A plurality of waveguide antenna units are arranged in a planar sparse array manner to obtain a planar sparse array layout diagram; wherein, the planar sparse array uses the working plane as a reference plane; it can be understood that the planar sparse array is a conventional sparse array method, which is well known to those skilled in the art and will not be repeated here. Figure 5A planar sparse array layout diagram obtained after simulation optimization of a planar waveguide array antenna in a specific embodiment is provided; Figure 6 For Figure 5 The schematic diagram of the planar waveguide sparse array antenna structure is formed based on the electromagnetic simulation software. Figure 6 The simulation is performed to obtain the scanning pattern of the planar waveguide sparse array antenna, as shown in Figure 7 As shown, the normal pointing direction is 0°, the normal gain of the planar waveguide sparse array antenna at 93 GHz is 25.54 dBi, the side lobe is 15.67 dB, and the radiation pattern drops to 1.26 dB when scanning to 20°.

[0068] Will Figure 5 The position of each array element in the planar sparse array layout diagram is mapped one by one to the inclined plane to obtain an inclined sparse array layout diagram, wherein the position of the array element is the position where the waveguide antenna unit is placed, and the inclined plane is a plane inclined at a first inclined angle to the reference plane. Figure 8 The schematic diagram is a principle diagram of the mapping relationship from a planar sparse array to a tilted sparse array. Arrange a plurality of waveguide antenna units according to the tilted sparse array layout diagram; then simulate the antenna array formed after the arrangement according to the tilted sparse array layout diagram, optimize and adjust the position of each array element, and obtain a lower tilted array sidelobe level. The final tilted sparse array layout diagram is as follows: Fig. 9 As shown, according to Figure 8 and Fig. 9 It can be seen that the density of array elements in the inclined sparse array layout diagram is greater than the density of array elements in the planar sparse array layout diagram. Fig.10 Schematic diagram of the tilted waveguide sparse array antenna structure.

[0069] based on Fig.10 The tilted waveguide sparse array antenna structure provided is simulated using electromagnetic software. Fig.11 The scanning radiation pattern of the tilted sparse array antenna at a frequency of 92 GHz is shown. The normal gain of the antenna at 92 GHz is 25.74 dBi, the side lobe is 15.56 dB, and the radiation pattern drops to 1.2 dB when scanning to 20°. Fig.12 The scanning radiation pattern of the tilted sparse array antenna with a frequency of 93 GHz is shown. The normal gain of the antenna at 93 GHz is 25.77 dBi, the side lobe is 15.84 dB, and the radiation pattern drops to 1.21 dB when scanning to 20°. Fig.13 The scanning radiation pattern of the tilted sparse array antenna with a frequency of 94 GHz is shown. The normal gain of the antenna at 94 GHz is 25.81 dBi, the side lobe is 16.13 dB, and the radiation pattern drops to 1.18 dB when scanning to 20°.

[0070] Since the radiation aperture of the tilted sparse array antenna is tilted, the direction of maximum radiation energy is in the tilted direction of the array. Figure 11 to Figure 13 The scanning radiation patterns of the tilted sparse array antenna at different frequencies show that the normal pointing direction of the radiation pattern of the tilted sparse array antenna is offset by 20°, and a 20° angle scan is achieved, and the side lobes and gain performance are normal.

[0071] Table 1 is a comparison table of the radiation pattern performance of a conventional planar sparse array and a tilted sparse array with the same number of array elements at a frequency of 93 GHz. Compared with the performance of a planar sparse array antenna, the tilted sparse array antenna has good radiation pattern gain, side lobe and scanning drop.

[0072] Table 1 Antenna performance comparison

[0073] Antenna type Antenna normal gain (dB) Sidelobe level (dB) Scan ±20° gain drop (dB) Planar sparse array 25.54 15.67 1.26 Slanted sparse array 25.77 15.84 1.21

[0074] Fig.14 The side view of the sparse array antenna with normal beam tilt in some embodiments of the present disclosure, wherein only the antenna radiation aperture is tilted, and the antenna radiation aperture matching layer is tilted 20° to the horizontal plane. Figure 1 The traditional antenna tilt model shown has an obviously smaller cross-sectional height, and as the height of the antenna array is reduced, the weight of the entire system is reduced.

[0075] Apart from Figure 2 In addition to the configuration method of tilting the antenna radiation aperture provided in the illustrated embodiment, other configuration methods are also provided in other embodiments, such as Fig.15 As shown, the first metal cavity 1 includes a straight waveguide section 12 and an inclined waveguide section 13, one end of the straight waveguide section 12 is arranged on a working plane to receive a radio frequency signal, and the arrangement direction of the straight waveguide section 12 is perpendicular to the working plane, the inclined waveguide section 13 is connected to the other end of the straight waveguide section 12, and the arrangement direction of the inclined waveguide section 13 forms a first inclined angle with the arrangement direction of the straight waveguide section 12, and the inclined waveguide section 13 is connected to the second metal cavity 2; the normal offset of the normal radiation pattern of the unit antenna can also be achieved. Fig.16 Based on Fig.15 The tilted waveguide sparse array antenna structure is formed.

[0076] Figures 17 to 19 Shown Fig.16 The scanning radiation patterns of the phased array antenna at different frequencies are shown. Since the radiation aperture of the antenna array is tilted, the direction of maximum radiation energy is in the tilted direction of the array. It can also achieve 20° angle scanning, and the side lobes and gain performance are normal.

[0077] It is understandable that those skilled in the art can also Figure 2 and Fig.15Set other ways to tilt the antenna radiation aperture, such as Figure 2 and Fig.15 The combination is performed by providing an inclined waveguide section and also providing an inclined mounting surface at the end of the inclined waveguide section.

[0078] In some embodiments, in order to enable the sparse array antenna to be applied to certain high-frequency scenarios, due to the large size of the air waveguide, the waveguide antenna unit in the form of an air waveguide can be replaced with a waveguide antenna unit in the form of a ridge waveguide. Fig. 20 shown.

[0079] In other embodiments, in order to enable the sparse array antenna to be applied to certain high-frequency scenarios, the waveguide antenna unit in the form of an air waveguide may be replaced with a waveguide antenna unit in the form of a dielectric-filled waveguide due to the large size of the air waveguide. The waveguide antenna unit in the form of a dielectric-filled waveguide may be replaced with a waveguide antenna unit in the form of a dielectric-filled waveguide. Fig.21 As shown, a suitable medium is filled in the metal cavity to achieve a reduction in the waveguide size.

[0080] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A sparse array antenna with tilted normal beam, characterized in that: include: A waveguide antenna unit, wherein the plurality of waveguide antenna units adopt the same open waveguide antenna structure, wherein the waveguide antenna unit comprises a first metal cavity and a second metal cavity that are connected, wherein one end of the first metal cavity is arranged on a working plane and receives a radio frequency signal, and the first metal cavity and the second metal cavity that are connected form a propagation path of the radio frequency signal; The radiation port of the waveguide antenna unit is arranged at one end of the second metal cavity away from the first metal cavity; the plane where the radiation port is located forms a first tilt angle with the working plane, so that the antenna pattern of the waveguide antenna unit is normally offset at the first tilt angle; Among them, several waveguide antenna units are arranged in a sparse array.

2. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The ends of the first metal cavities of the plurality of waveguide antenna units are arranged on the same working plane; The heights of the plurality of waveguide antenna units are equal.

3. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The method of arranging a plurality of waveguide antenna elements in a sparse array includes: Arranging a plurality of waveguide antenna units in a planar sparse array manner to obtain a planar sparse array layout diagram; wherein the planar sparse array uses the working plane as a reference plane; Mapping the position of each array element in the planar sparse array layout diagram to the inclined plane one by one to obtain an inclined sparse array layout diagram, wherein the position of the array element is the position where the waveguide antenna unit is placed, and the inclined plane is a plane inclined at a first inclined angle to the reference plane; Arrange a plurality of the waveguide antenna units according to a tilted sparse array layout diagram.

4. The sparse array antenna with normal beam tilt according to claim 3, characterized in that: The density of array elements in the inclined sparse array layout diagram is greater than the density of array elements in the planar sparse array layout diagram.

5. The sparse array antenna with normal beam tilt according to claim 3, characterized in that: The method of arranging the plurality of waveguide antenna units in a sparse array also includes: The antenna array formed after being arranged according to the tilted sparse array layout diagram is simulated to optimize and adjust the position of each array element.

6. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The first metal cavity has an inclined assembly surface at one end close to the second metal cavity, and the inclined assembly surface forms a first inclined angle with the working plane. The second metal cavity is assembled on the inclined assembly surface so that the plane where the radiation port is located forms a first inclined angle with the working plane.

7. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The first metal cavity comprises a straight waveguide section and an inclined waveguide section, one end of the straight waveguide section is arranged on a working plane to receive a radio frequency signal, and an arrangement direction of the straight waveguide section is perpendicular to the working plane, the inclined waveguide section is connected to the other end of the straight waveguide section, and an arrangement direction of the inclined waveguide section forms a first inclined angle with an arrangement direction of the straight waveguide section, and the inclined waveguide section is connected to the second metal cavity.

8. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The second metal cavity adopts an impedance gradient structure; And, the aperture of the second metal cavity is larger than that of the first metal cavity.

9. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The waveguide antenna unit adopts an air waveguide form, a ridge waveguide form, or a dielectric-filled waveguide form.

10. The sparse array antenna with normal beam tilt according to claim 1, characterized in that: The first inclination angle is greater than 0 degree and less than or equal to 20 degrees.

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