A W-band feed horn antenna based on an inclined plane axial corrugation structure

Abstract

A W-band feed horn antenna based on an inclined-plane axial corrugation structure, comprising a rectangular waveguide, a rectangular-circular conversion structure, and a circular waveguide sequentially arranged from bottom to top. The inner wall of the circular waveguide is loaded with a corrugated groove structure, which is composed of a number of annular corrugated grooves engraved on the inner wall of the circular waveguide to improve the cross-polarization discrimination of the feed horn antenna. A corrugation structure is loaded at the radiation aperture of the circular waveguide, which is located above the corrugated groove structure and consists of multiple turns of corrugations. Except for the outermost turn of corrugations, the outer sidewalls of the remaining turns of corrugations all adopt an inclined-plane structure with a certain inclination angle. The corrugation structure is used to stabilize the gain of the feed horn antenna and improve the rotationally symmetric radiation characteristics of the feed horn antenna. The present invention achieves stable gain, high cross-polarization discrimination, stable half-power beamwidth, and rotationally symmetric radiation characteristics in the frequency range of 75 GHz to 110 GHz.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and particularly relates to a W-band feed horn antenna based on an inclined axial corrugation structure, which can be used in a compact range measurement system. Background Art

[0002] With the development of millimeter-wave radar, terahertz detection and stealth technology, traditional far-field and near-field tests are no longer applicable to antenna tests in these fields. Compact range measurement is an antenna measurement method that measures the antenna to be tested by generating a quasi-plane wave in a smaller space. Due to its advantages such as small size, short time consumption, simple alignment, strong confidentiality, and low climate requirements, when testing some millimeter-wave and higher-frequency antennas, a compact range test system is often selected.

[0003] A compact range test system usually consists of a feed and a reflector. As an important part of the whole system, the performance of the feed will directly affect the performance of the whole measurement system. Usually for the feed, we hope that its amplitude pattern has a rotationally symmetric radiation performance. At the same time, a lower voltage standing wave ratio, stable gain, stable half-power beam width, and higher cross-polarization discrimination are also required.

[0004] Currently, the axial corrugated horn antenna is the most common form of the compact range feed. In 2017, K. Sambasivarao designed a high-performance compact range feed. This feed uses the corrugation form of axial corrugations, with a total of seven turns of corrugations, a gain of 14 dBi. In the operating frequency range, the gain fluctuates by 1 dBi, and the half-power beam width is between 32° and 41°, with a fluctuation of 9°. The cross-polarization discrimination is better than 50 dB. The gain and half-power beam width of this feed have large fluctuations in the operating frequency range; the W-band compact range feed produced by MVG also uses the corrugation form of axial corrugations, and the half-power beam width is 34° - 40°. Compared with the high-performance compact range feed designed by K. Sambasivarao, it has a more stable half-power beam width, but the cross-polarization discrimination is only 37 dB. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a W-band feed horn antenna based on an inclined axial corrugation structure, which mainly solves the problems such as unstable gain and half-power beam width of the existing compact range feed, and low cross-polarization discrimination, and improves the test performance of the whole compact range test system from the perspective of improving the feed performance. The designed feed horn antenna realizes stable gain, high cross-polarization discrimination, stable half-power beam width, and rotationally symmetric radiation characteristics in the frequency range of 75 GHz to 110 GHz.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A W-band feed horn antenna based on an inclined axial corrugated structure comprises a rectangular waveguide, a rectangular-circular conversion structure and a circular waveguide arranged in sequence from bottom to top, wherein:

[0008] The inner wall of the circular waveguide is loaded with a corrugated groove structure, the corrugated groove structure is composed of a plurality of annular corrugated grooves, the corrugated grooves are engraved on the inner wall of the circular waveguide, and the corrugated groove structure is used to improve the cross-polarization discrimination of the feed horn antenna;

[0009] The radiation port of the circular waveguide is loaded with a corrugated structure, which is located above the corrugated groove structure and consists of multiple circles of corrugations. Except for the outermost circle of corrugations, the outer side walls of the remaining circles of corrugations all adopt an inclined structure with a certain inclination angle. The outer side wall is the corrugated wall on the side of each circle of corrugations away from the central axis. The inclination angle is the angle between the outer side wall of the corrugation and the horizontal plane. The corrugated structure is used to stabilize the gain of the feed horn antenna and improve the rotationally symmetric radiation characteristics of the feed horn antenna.

[0010] In one embodiment, the rectangular-circular conversion structure is in a stepped shape, used for transition between a rectangular waveguide and a circular waveguide, and is composed of multiple levels of equal-height rectangular waveguides with unchanged wide sides and increasing narrow sides from bottom to top. The wide side refers to the wide side direction along the mouth of the rectangular waveguide, and the narrow side refers to the narrow side direction along the mouth of the rectangular waveguide.

[0011] In one embodiment, the rectangular-circular conversion structure is from the first step to the fifth step from bottom to top, and the narrow side lengths of each step are b1, b2, b3, b4, and b5, respectively, and meet the following conditions: 1.27 mm <b1<b2<b3<b4<b5<2.69mm,第一级阶梯到第五级阶梯的宽边长度均与所述矩形波导的口面的宽边长度保持一致;第一级阶梯到第四级阶梯的内部的直角侧边均有圆角结构,圆角半径介于0.2mm~0.3mm之间,第五级阶梯内部的直角侧边的圆角尺寸与圆波导的半径保持一致。

[0012] In one embodiment, the corrugated groove structure has three circles of corrugated grooves, each circle of corrugated grooves has the same size, and the radius of the corrugated groove is r, 1.65 mm <r<2mm,电尺寸在0.4λ c ~0.5λ c Between c is the wavelength corresponding to the cut-off frequency.

[0013] In one embodiment, the axial height of each turn of the corrugated grooves is the same, which is h, the spacing between adjacent corrugated grooves is l, and l = h is satisfied. The distance between the lowermost corrugated groove and the bottom surface of the circular waveguide is f, and 1 mm < f < 5.7 mm.

[0014] In one embodiment, the corrugated structure is composed of five turns of axial corrugations with non - common bottom surfaces. The axial corrugations are a corrugation form composed of multiple turns of coaxial circular grooves. From the inside to the outside, they are the first turn to the fifth turn of corrugations, and the corrugations of each turn increase in sequence;

[0015] Among them, the thicknesses of the tops of the walls of the first turn to the fifth turn of corrugations are t1, t2, t3, t4, t5 respectively, and t1 = t2 = t3 = t4 < t5; the groove width of the corrugations is w i , 0.25 mm < w i <0.35 mm, and the groove width is the distance between adjacent corrugations; the depth of each turn of corrugations is d i , 1.31 mm < d i <1.41 mm.

[0016] In one embodiment, the inclination angle of the inclined plane structure is θ, and 0° < θ < 90°.

[0017] In one embodiment, a choke ring structure is loaded on the outer surface of the corrugated structure. The choke ring structure is a circular groove coaxial with the corrugated structure, and the choke ring structure is used to further stabilize the gain of the feed horn antenna.

[0018] In one embodiment, the aperture plane of the choke ring structure is slightly lower than the aperture plane of the outermost turn of corrugations.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] First, by loading the axial corrugated structure and the choke ring structure at the radiation aperture plane, the gain of the feed horn antenna is between 13.5 dBi and 13.9 dBi in the frequency range of 75 GHz to 110 GHz, and the gain fluctuates by 0.4 dBi, and the gain stability is good.

[0021] Second, by reasonably adjusting the structural parameters such as the depth, width of the corrugated grooves of the choke ring and the axial corrugations, and the thickness of the corrugated walls, the E - plane half - power beam width of the feed horn antenna is 35.06° to 40.47° in the frequency range of 75 GHz to 110 GHz, and the fluctuation is only 5.41°, and the H - plane half - power beam width is 35.93° to 41.6°, and the fluctuation is only 5.67°.

[0022] Thirdly, by loading a corrugated groove structure on the inner wall of the circular waveguide, the present invention suppresses the propagation and cross polarization of higher-order modes, thereby improving the cross-polarization discrimination. In the frequency range of 75 GHz to 110 GHz, the cross-polarization discrimination of the feed horn antenna in the E-plane and H-plane is greater than 50 dB.

[0023] Fourthly, by designing the side wall of the corrugation as an inclined surface structure with a certain inclination angle, the physical strength of the corrugation structure is significantly improved without affecting the performance of the feed horn antenna. Description of the Drawings

[0024] Figure 1 is a schematic structural diagram of a W-band feed horn antenna based on an inclined surface axial corrugation structure of the present invention.

[0025] Figure 2 is a structural sectional view of the XOZ section of a W-band feed horn antenna based on an inclined surface axial corrugation structure of the present invention, where 51 is the inclined surface side wall structure of the corrugation.

[0026] Figure 3 is a structural sectional view of the YOZ section of a W-band feed horn antenna based on an inclined surface axial corrugation structure of the present invention, where 51 is the inclined surface side wall structure of the corrugation.

[0027] Figure 4 is a sectional view of a stepped rectangular-to-circular conversion structure of the present invention.

[0028] Figure 5 is a sectional view of the corrugated groove structure of the present invention.

[0029] Figure 6 is a sectional view of the corrugation structure of the present invention.

[0030] Figure 7 is a schematic diagram of the voltage standing wave ratio of the present invention.

[0031] Figure 8 is a schematic diagram showing the variation of the gain with frequency of the present invention.

[0032] Figure 9 is a schematic diagram showing the variation of the E-plane and H-plane half-power beam widths with frequency of the present invention.

[0033] Figure 10 is a schematic diagram of the E-plane main polarization and cross polarization at different frequencies of the present invention.

[0034] Figure 11 is a sectional view of the corrugation structure of the present invention.

[0035] Figure 12 is the polar coordinate pattern of the E-plane and H-plane at 75 GHz, 90 GHz, and 110 GHz of the present invention. Detailed implementation manners

[0036] In order to make the objectives, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it shall not be used as a basis for any limitation to the present invention.

[0037] The W-band feed horn antenna of the present invention is based on an inclined plane axial corrugation structure and operates in the W band. Specifically, referring to Figure 1 , its main body mainly includes, from bottom to top, a rectangular waveguide 1, a rectangular-circular conversion structure 2, and a circular waveguide 3 arranged in sequence, and a corrugated slot structure 4 and a corrugation structure 5 are loaded on the circular waveguide 3, and a choke ring structure 6 can be further loaded outside the corrugation structure 5.

[0038] Among them, the corrugated slot structure 4 is used to improve the cross-polarization discrimination of the feed horn antenna. It is loaded on the inner wall of the circular waveguide 3 and is composed of several annular corrugated slots, and these corrugated slots are all engraved on the inner wall of the circular waveguide 3.

[0039] The corrugation structure 5 is used to stabilize the gain of the feed horn antenna and improve the rotationally symmetric radiation characteristics of the feed horn antenna. It is loaded at the radiation aperture surface of the circular waveguide 3. The corrugation structure 5 is located above the corrugated slot structure 4 and is composed of multiple turns of corrugations. Here, multiple turns means multiple turns distributed in sequence from the inside to the outside. In the corrugation structure 5, except for the outermost turn of corrugations, the outer side walls of the remaining turns of corrugations all adopt an inclined plane structure 5-1 with a certain inclination angle. In the present invention, the upper part is defined as "outer" and the lower part is defined as "inner", the outer side wall is defined as the corrugation wall on the side of each turn of corrugations away from the central axis, and the inclination angle is defined as the angle between the outer side wall of the corrugation and the horizontal plane (i.e., Figure 1 the xoy plane in

[0040] The principle of the present invention is as follows: First, a good transition between the rectangular waveguide 1 of the feeding section and the circular waveguide 3 in terms of structure and impedance is realized through the rectangular-circular conversion structure 2; then, by loading the corrugated slot structure 4 inside the circular waveguide 1, the suppression of cross polarization is realized, thereby improving the cross-polarization discrimination of the feed horn antenna; then, by loading the corrugation structure 5, high-order modes are introduced, thereby realizing the rotationally symmetric radiation characteristics of the feed horn antenna. And in the corrugation structure 5, the outer side walls of the remaining turns of corrugations except for the outermost turn of corrugations all adopt an inclined plane structure 5-1 with a certain inclination angle. Without affecting the performance of the feed horn antenna, the physical strength of the corrugation structure is improved, thereby avoiding the influence on the performance caused by the deformation of the corrugation structure during processing and use; finally, a choke ring structure 6 is loaded outside the corrugation structure. The choke ring 6 is a circular ring groove coaxial with the corrugation structure 5. By increasing the area of the radiation aperture surface, the problem of low gain of the feed horn antenna at low frequencies is solved, making the gain of the feed horn antenna more stable throughout the W band.

[0041] Reference Figure 2 、 Figure 3 In the embodiments of the present invention, the size of the wide side a of the rectangular waveguide 1 is mainly determined by the cut-off frequency, and generally needs to satisfy 2a > λ c , and the size of its narrow side b should be less than or equal to about half of the wide side a. Exemplarily, the wide side a is taken as 2.69 mm, the narrow side b is taken as 1.27 mm, and the axial length L is 6.65 mm. The four right-angled side edges of the inner wall of the rectangular waveguide 1 all have rounded corner structures, and the radius of the rounded corners can be set to 0.2 mm.

[0042] In order to enable the circular waveguide 3 to operate in the operating frequency band of the rectangular waveguide 1, the radius R of the circular waveguide 3 should satisfy:

[0043]

[0044] In this embodiment, R is taken as 1.65 mm, and the axial length L1 of the circular waveguide 3 is taken as 6.65 mm.

[0045] The rectangular-to-circular conversion structure 2 is used for the transition between the rectangular waveguide 1 and the circular waveguide 3. Reference Figure 4 , in the embodiments of the present invention, it is of a stepped shape and is composed of multiple equal-height rectangular waveguides with the wide side unchanged and the narrow side increasing from bottom to top to achieve a smooth transition of impedance. The wide side mentioned here refers to the direction of the wide side along the mouth surface of the rectangular waveguide 1, and the narrow side refers to the direction of the narrow side along the mouth surface of the rectangular waveguide 1.

[0046] The number of stages N of this embodiment is determined by the characteristic impedances of the rectangular waveguide 1 and the circular waveguide 3 in the feeding section and the maximum voltage standing wave ratio, and can be expressed by the following formula:

[0047]

[0048] In the formula, K is the impedance ratio of the rectangular waveguide to the circular waveguide, and ρ max is the maximum voltage standing wave ratio.

[0049] In this embodiment, N = 5 is taken. From bottom to top, the equal-height rectangular waveguides are sequentially defined as the first-stage step to the fifth-stage step, and the narrow-side lengths of each stage of the step are b1, b2, b3, b4, and b5 in sequence. Then, the relationship between the narrow sides of each stage of the rectangular waveguide can be expressed by the following formula:

[0050]

[0051] In this embodiment, the following conditions are met: 1.27 mm <b1<b2<b3<b4<b5<2.69mm,各级阶梯的宽边长度均与矩形波导1的口面的宽边长度保持一致,为a,即2.69mm,窄边长度递增,分别为:第一级阶梯窄边长度b1为1.46mm,第二级阶梯窄边长度b2为1.68mm,第三级阶梯窄边长度b3为1.92mm,第四级阶梯窄边长度b4为2.21mm,第五级阶梯窄边长度b5为2.54mm,第一级至第五级矩形波导的长度均为工作频带中心频率对应的波导波长的1 / 4,即l1=l2=l3=l4=l5=1.07mm。五级矩形波导的内部的所有直角侧边均有圆角结构,前四级矩形波导的圆角半径介于0.2mm~0.3mm之间,并优选为与矩形波导1内壁的圆角半径一致,即优选为0.2mm,第五级矩形波导内部的直角侧边的圆角尺寸与圆波导3的半径尺寸一致。

[0052] Reference Figure 5 In the embodiment of the present invention, the corrugated groove structure 4 has three circles of corrugated grooves, each circle of corrugated grooves has the same size, the axial height of each circle of corrugated grooves is h, the spacing between adjacent corrugated grooves is l, and l = h = 0.2mm, wherein the distance f between the bottom corrugated groove and the bottom surface of the circular waveguide 3 is between 1mm and 5.7mm, preferably 3mm. The radius of each circle of corrugated grooves is r, 1.65mm <r<2mm,电尺寸在0.4λ c ~0.5λ c Between c is the wavelength corresponding to the cut-off frequency, and in this embodiment, r=1.85 mm.

[0053] Reference Figure 6 In an embodiment of the present invention, the corrugation form of the corrugated structure 5 is an axial corrugation, and the axial corrugation is a corrugation form composed of multiple circles of coaxial circular grooves, so that the feed horn antenna can produce a stable gain while maintaining good radiation characteristics. The corrugated structure 5 has a total of five circles, from the first circle to the fifth circle of corrugations from the inside to the outside, and each circle of corrugations rises successively. Preferably, in order to make the gain and beam width within the entire frequency band more stable, each circle of corrugations does not share the same bottom surface. Among them, the groove depth, groove width and corrugation wall thickness of each circle of corrugations are not exactly the same. Specifically, the thickness of the top of the corrugated wall from the first circle to the fifth circle of corrugations are t1, t2, t3, t4, t5, respectively, and satisfy t1=t2=t3=t4. <t5;波纹的槽宽为w i , 0.25mm <w i <0.35mm, where the groove width is the distance between adjacent corrugations; the depth of each corrugation is d i , 1.31mm <di <1.41 mm.

[0054] More specifically, the depth d1 of the first circle of corrugations is 1.41 mm, the groove width w1 is 0.25 mm, and the thickness t1 of the top of the corrugated wall is 0.15 mm; the depth d2 of the second circle of corrugations is 1.37 mm, the groove width w2 is 0.2 mm, the thickness t2 of the top of the corrugated wall is 0.15 mm, and the height z1 of the step is 0.47 mm; the depth d3 of the third circle of corrugations is 1.34 mm, the groove width w3 is 0.2 mm, the thickness t3 of the top of the corrugated wall is 0.15 mm, and the height z2 of the step is 0.47 mm; the depth d4 of the fourth circle of corrugations is 1.33 mm, the groove width w4 is 0.15 mm, the thickness t4 of the top of the corrugated wall is 0.15 mm, and the height z3 of the step is 0.47 mm; the depth d5 of the fifth circle of corrugations is 1.31 mm, the groove width w5 is 0.2 mm, the thickness t5 of the corrugated wall is 0.42 mm, and the height z4 of the step is 0.47 mm.

[0055] Furthermore, in order to strengthen the physical strength of the corrugated wall without affecting the performance of the feed horn antenna, the outer side walls of the first to fourth circles of corrugations from the inside to the outside adopt an inclined surface structure 5-1 with an inclination angle θ, 0° < θ < 90°, and preferably θ = 80°.

[0056] In the embodiment of the present invention, referring to Figure 1 , a choke ring structure 6 is also loaded on the outer surface of the corrugated structure 5. The choke ring structure 6 is a circular ring groove coaxial with the corrugated structure 5, which is used to improve the gain at low frequencies and further stabilize the gain of the feed horn antenna in the entire frequency band. More specifically, referring to Figure 6 , the choke ring structure 6 is loaded outside the outermost circle of corrugations of the corrugated structure 5, can be located on the end face, and its aperture surface is slightly lower than the aperture surface of the outermost circle of the corrugated structure. The groove width w6 of the choke ring is 0.3 mm, the groove depth d6 of the choke ring is 1.1 mm, and the wall thickness t6 of the choke ring is 0.42 mm.

[0057] In this embodiment, a W-band feed horn antenna based on an inclined surface axial corrugated structure is designed. It operates in the W-band and has good gain and beam width stability, high cross-polarization discrimination, rotationally symmetric radiation characteristics, and stable half-power beam width.

[0058] The effects of the present invention can be further illustrated by the following simulations:

[0059] As Figure 7 shown, it is a schematic diagram of the voltage standing wave ratio of a stable beam feed horn antenna based on a transverse slot corrugated ridge structure in this embodiment. In the range of 75 GHz to 110 GHz, the voltage standing wave ratio is less than 1.3, having a good matching effect.

[0060] As shown Figure 8 in the figure, it is a graph showing the variation of the gain of a W-band feed horn antenna with a bevel axial corrugation structure in this embodiment. In the range of 75 GHz to 110 GHz, the gain is between 13.5 dBi and 13.9 dBi, with a gain fluctuation of 0.4 dBi, indicating good gain stability.

[0061] As shown Figure 9 in the figure, it is a graph showing the variation of the E-plane and H-plane half-power beam widths of a W-band feed horn antenna with a bevel axial corrugation structure in this embodiment. In the range of 75 GHz to 110 GHz, the E-plane half-power beam width is between 35.06° and 40.47°, with a fluctuation of only 5.41°, and the H-plane half-power beam width is between 35.93° and 41.6°, with a fluctuation of only 5.67°. The half-power beam widths are very stable in both the E-plane and H-plane.

[0062] As shown Figure 10 in the figure, it is the E-plane co-polarization and cross-polarization patterns of a W-band feed horn antenna with a bevel axial corrugation structure in this embodiment at different frequencies. In the range of 75 GHz to 110 GHz, the E-plane co-polarization directions Figure 1 at different frequencies have good consistency, and the cross-polarization discrimination of the E-plane is higher than 50 dB.

[0063] As shown Figure 11 in the figure, it is the H-plane co-polarization and cross-polarization patterns of a W-band feed horn antenna with a bevel axial corrugation structure in this embodiment at different frequencies. In the range of 75 GHz to 110 GHz, the H-plane co-polarization directions Figure 1 at different frequencies have good consistency, and the cross-polarization discrimination of the H-plane is higher than 50 dB.

[0064] As shown Figure 12 in the figure, it is the polar coordinate pattern of a W-band feed horn antenna with a bevel axial corrugation structure in this embodiment. When the frequencies are 75 GHz, 90 GHz, and 110 GHz, the radiation patterns of the E-plane and H-plane of the feed horn antenna have good fitting degrees.

[0065] In summary, for the feed horn antenna of the present invention, the rectangular waveguide and the circular waveguide are connected through a rectangular-circular conversion structure, achieving a good transition in both structure and impedance; by loading corrugated grooves around the inner wall of the circular waveguide, the higher-order modes and cross-polarization are suppressed, thus improving the cross-polarization discrimination; by loading an axial corrugation structure on the radiation aperture surface and optimizing the size parameters such as the depth of the corrugation, the groove width, and the thickness of the corrugated wall, the feed horn antenna generates a stable gain while maintaining good radiation characteristics. Considering that the wall thickness of the corrugation in the W band is too thin and is prone to deformation during processing and use, which affects the performance of the feed, therefore, the present invention adopts a bevel structure with an 80° inclination angle on the side surfaces of the first to fourth turns of the axial corrugation, improving the physical strength of the corrugated structure without affecting the performance of the feed; by loading a choke ring structure outside the corrugated structure, the gain at low frequencies is significantly improved, further improving the stability of the gain of the feed horn antenna.

[0066] The above has introduced in detail a W-band feed horn antenna based on a bevel axial corrugation structure, and elaborated and implemented the principle and implementation mode of the present invention with a detailed structural design. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A W-band feed horn antenna based on an inclined plane axial corrugated structure, comprising a rectangular waveguide (1), a rectangular-circular transition structure (2), and a circular waveguide (3) sequentially arranged from bottom to top, characterized in that: A corrugated groove structure (4) is loaded on the inner wall of the circular waveguide (3). The corrugated groove structure (4) is composed of several annular corrugated grooves. The corrugated grooves are engraved on the inner wall of the circular waveguide (3). The corrugated groove structure (4) is used to improve the cross-polarization discrimination of the feed horn antenna; A corrugated structure (5) is loaded at the radiation aperture surface of the circular waveguide (3). The corrugated structure (5) is located above the corrugated groove structure (4) and is composed of multiple turns of corrugations. Except for the outermost turn of corrugations, the outer side walls of the remaining turns of corrugations all adopt an inclined plane structure (5-1) with a certain inclination angle. The outer side wall is the corrugated wall on the side of each turn of corrugation away from the central axis. The inclination angle is the angle between the corrugated outer side wall and the horizontal plane. The corrugated structure (5) is used to stabilize the gain of the feed horn antenna and improve the rotationally symmetric radiation characteristics of the feed horn antenna.

2. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 1, characterized in that The rectangular-circular transition structure (2) is of a stepped shape and is used for the transition between the rectangular waveguide and the circular waveguide. It is composed of multiple levels of equal-height rectangular waveguides with the wide side unchanged and the narrow side increasing from bottom to top. The wide side refers to the direction of the wide side along the aperture surface of the rectangular waveguide (1), and the narrow side refers to the direction of the narrow side along the aperture surface of the rectangular waveguide (1).

3. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 2, characterized in that, The rectangular-circular transition structure (2) is successively the first-level step to the fifth-level step from bottom to top. The narrow side lengths of each level of step are b1, b2, b3, b4, and b5 in sequence, and satisfy: 1.27 mm < b1 < b2 < b3 < b4 < b5 < 2.69 mm. The wide side lengths of the first-level step to the fifth-level step are all consistent with the wide side length of the aperture surface of the rectangular waveguide (1); the inner right-angled side edges of the first-level step to the fourth-level step all have a rounded corner structure, and the radius of the rounded corner is between 0.2 mm and 0.3 mm. The rounded corner size of the inner right-angled side edge of the fifth-level step is consistent with the radius of the circular waveguide (3).

4. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 1, characterized in that, The corrugated grooves of the corrugated groove structure (4) have a total of three turns, and the dimensions of the corrugated grooves in each turn are the same. The radius of the corrugated groove is r, where 1.65 mm < r < 2 mm, and the electrical size is between 0.4λ c ~0.5λ c and λ c is the wavelength corresponding to the cut-off frequency.

5. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 4, characterized in that, The axial heights of each turn of the corrugated grooves are the same, which is h. The distance between adjacent corrugated grooves is l, and l = h. The distance between the lowermost corrugated groove and the bottom surface of the circular waveguide (3) is f, and 1 mm < f < 5.7 mm.

6. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 1, wherein The corrugated structure (5) is composed of five turns of non-coplanar axial corrugations. The axial corrugations are a form of corrugations composed of multiple turns of coaxial circular grooves. From the inside to the outside, they are the first turn to the fifth turn of corrugations, and each turn of corrugation rises in sequence; Among them, the thicknesses of the tops of the first to fifth corrugated walls are t1, t2, t3, t4, and t5 respectively, and satisfy t1 = t2 = t3 = t4 < t5; the groove width of the corrugation is w i , 0.25mm < w i < 0.35mm, and the groove width is the distance between adjacent corrugations; the depth of each corrugation is d i , 1.31mm < d i < 1.41mm.

7. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 1 or 6, characterized in that, The inclination angle of the inclined plane structure (5-1) is θ, and 0° < θ < 90°.

8. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 1, wherein A choke ring structure (6) is loaded on the outer surface of the corrugated structure (5). The choke ring structure (6) is a circular groove coaxial with the corrugated structure (5). The choke ring structure (6) is used to further stabilize the gain of the feed horn antenna.

9. The W-band feed horn antenna based on the inclined plane axial corrugation structure according to claim 8, characterized in that, The aperture surface of the choke ring structure (6) is slightly lower than the aperture surface of the outermost turn of corrugations.

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