Wideband circularly polarized waveguide slot antenna and antenna array

Abstract

The application provides a broadband circularly polarized waveguide slot antenna and an antenna array, the waveguide slot antenna comprising a waveguide body, two parallel rows of backrest waveguide walls are arranged on the A side of the waveguide body; the backrest waveguide walls in the same row are arranged at intervals; characterized in that, an inclined slot is arranged on the B side of each backrest waveguide wall away from the A side; a bending slot is arranged between the two backrest waveguide walls in the same row on the A side, the bending slot comprising a radiation part Lf1 and a non-radiation part Lf2; the bending slots in the same row are arranged at intervals with the inclined slots; the inclined directions of the two rows of inclined slots are consistent; the two bending slots in the two rows of bending slots are arranged in a 180° symmetry centering on the end part of the Lf2 part; the centers of the two rows of bending slots and the centers of the two rows of inclined slots are in the same section of the L-shaped waveguide body and the backrest waveguide wall. The application does not have strict requirements on the width of the backrest waveguide wall and the inclined angle of the inclined slot. The inclined angle θ of the slot can be freely set within a certain range according to the actual situation, the Lf1 part of the bending slot is at a 90° angle with the Lf1 part, the length of the two parts of the bending slot Lf1 and Lf2 is adjusted to realize two orthogonal polarization equal amplitudes, the antenna design process is simple and has high freedom.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, specifically to a broadband circularly polarized waveguide slot antenna and antenna array. Background Technology

[0002] Existing circularly polarized antennas are mainly microstrip antennas, including microstrip patch antennas and microstrip slot antennas. These antennas can be combined in various ways according to the feed network and arrangement, making it easy to achieve circular polarization. Researchers have proposed many methods to achieve circular polarization and optimized impedance and axial ratio bandwidth. In addition, they are widely used due to their low profile, light weight, and ease of conformal application. However, microstrip antennas still have disadvantages such as low power capacity, low radiation efficiency, poor environmental adaptability, and high requirements for dielectric materials. Circularly polarized antennas constructed by combining printed dipoles and magnetoelectric dipoles can achieve a large operating bandwidth, but their structure is more complex, the manufacturing cost is higher, and similar to microstrip circularly polarized antennas, the antenna efficiency is affected by dielectric loss and feed line loss.

[0003] From a transmission line structure perspective, metallic waveguides and coaxial structures offer advantages in low loss. Waveguide slot antennas employ a centralized feeding structure, boasting advantages such as simple structure, easy fabrication, high structural strength, high efficiency, and large power capacity. Based on these advantages, waveguide slot antennas are widely used in radar applications. Current research on waveguide slot antennas primarily focuses on linearly polarized antennas. To achieve circularly polarized waveguide slot antennas, the following methods are commonly used: First, by generating two polarization components with a 90° phase difference in the traveling wave within the slot waveguide. Second, by introducing a circular polarizer on top of linear polarization to radiate circularly polarized waves. Third, by creating two different polarizations with a 90° phase difference through the slot shape and spatial spacing. Traveling wave arrays are frequency-scanning antennas with dispersive beam characteristics; introducing a circular polarizer increases the complexity of the antenna structure and typically results in a narrower operating bandwidth, failing to meet the ever-increasing communication capacity requirements. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to achieve a good wide bandwidth and facilitate the independent assembly of a large planar array of circularly polarized waveguide slot antennas based on a simple structural design.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] A broadband circularly polarized waveguide slot antenna includes a waveguide body with two parallel rows of back-to-back waveguide walls on side A of the waveguide body. The back-to-back waveguide walls in the same row are spaced apart. Each back-to-back waveguide wall has an inclined slot on its side B, away from side A. A bent slot is formed between the two back-to-back waveguide walls in the same row on side A. The bent slot includes a radiating portion Lf1 and a non-radiating portion Lf2. The bent slot and the inclined slot in the same row are spaced apart. The inclined directions of the two rows of inclined slots are consistent. Two adjacent bent slots in the two rows are symmetrically arranged with a 180° rotation around the end of the Lf2 portion. The centers of the two rows of bent slots and the two rows of inclined slots are located within the same cross-section of the L-shape formed by the waveguide body and the back-to-back waveguide walls.

[0007] Furthermore, the folded gap includes two parts: Lf2, which is parallel to the length direction of side A, and Lf1, which is orthogonal to the inclined gap. The Lf2 part does not cut the waveguide surface current and does not generate radiation, which is the non-radiative part; the Lf1 part cuts the surface current and forms orthogonal polarization with the inclined gap, which is the radiative part.

[0008] Furthermore, the inclined gaps in the same row are set at equal intervals.

[0009] Furthermore, the waveguide slot antenna is center-fed, and a groove 6 is used in the center of the waveguide body to separate the electric fields on both sides, so that the electric fields on both sides are symmetrically distributed.

[0010] Furthermore, the tilt angle of the tilted gap can be adjusted as needed.

[0011] Furthermore, the length of the inclined slit and the bent slit is 0.5 wavelengths.

[0012] Furthermore, the height of the back waveguide wall is 1 / 4 wavelength, the height of the waveguide cross-section is less than 0.2 wavelengths, and the length of the waveguide cross-section is less than 0.7 wavelengths.

[0013] Furthermore, the waveguide body and the back waveguide wall are made of metal or a composite material with a metal-plated surface.

[0014] Furthermore, the waveguide body is integrally formed with the back waveguide wall.

[0015] The present invention also provides an antenna array that uses the above-described antenna.

[0016] The advantages of this invention are:

[0017] 1. There are no strict requirements on the width of the back waveguide wall or the tilt angle of the inclined slot. The slot tilt angle θ can be freely set within a certain range according to the actual situation, and the bent slot Lf1 part can be at a 90° angle with it. By adjusting the lengths of the two bent slots Lf1 and Lf2, two orthogonal polarizations with equal amplitude can be achieved. The antenna design process is simple and has a high degree of freedom.

[0018] 2. By using the height difference of 1 / 4 wavelength between the inclined slit and the bent slit, two orthogonal modes with equal amplitude and a 90-degree phase difference are excited, and circularly polarized radiation waves are synthesized in space, achieving impedance matching and good axial ratio characteristics in a wide frequency band.

[0019] 3. This invention employs an all-metal waveguide integrated processing method, resulting in low loss, structural stability, and easy achievement of high radiation efficiency. It also features circular polarization characteristics, enabling the reception of electromagnetic waves of arbitrary polarization. It is suitable for airborne, spaceborne, and other platforms with stringent antenna stability requirements. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the antenna described in Embodiment 1 of the present invention;

[0021] Figure 2 This is a cross-sectional view of the L-shaped waveguide in Embodiment 1 of the present invention;

[0022] Figure 3 This is a top view of the antenna unit described in Embodiment 1 of the present invention;

[0023] Figure 4 This is a front view of the antenna unit described in Embodiment 1 of the present invention;

[0024] Figure 5 This is a simulation result diagram of the antenna impedance bandwidth of the antenna described in Embodiment 1 of the present invention;

[0025] Figure 6 This is a simulation result diagram of the axial ratio of the antenna described in Embodiment 1 of the present invention;

[0026] Figure 7 The simulation results of the far-field normalized radiation pattern of the antenna at the center frequency point as described in Embodiment 1 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment describes a broadband circularly polarized waveguide slot antenna, wherein the structural schematic of the circularly polarized waveguide slot antenna is shown below. Figure 1 and Figure 2 As shown, it includes: a metal waveguide body 1, and two parallel rows of back-to-back waveguide walls 5 on the same side of the center of the metal waveguide body 1 along the two-sided extension direction, with the back-to-back waveguide walls 5 in each row spaced apart. In this embodiment, the waveguide body and the back-to-back waveguide walls are integrally formed.

[0030] Each back-mounted waveguide wall 5 has an inclined slot 3, which cuts into the waveguide walls on both sides of the back-mounted waveguide wall 5. On the same row of back-mounted waveguide walls 5, a bent slot 2 is formed between two adjacent back-mounted waveguide walls 5, and the two rows of bent slots 2 are offset from the centerline of the metal waveguide body 1. The bent slots 2 and inclined slots 3 on each row are spaced apart, and the bent slots 2 between two rows are also spaced apart from the paired inclined slots 3. The center of the two rows of bent slots 2 and the center of the corresponding pair of inclined slots 3 are located within the same L-shaped cross-section of the metal waveguide 1.

[0031] The center 4 of the metal waveguide body 1 serves as the antenna input port. Both ends of the antenna are either closed short-circuited or connected to matched loads to form the main structure of the circularly polarized waveguide slot antenna. The metal waveguide body 1 is a hollow metal waveguide, or a composite material with a gold-plated surface. The design principle of this embodiment is as follows:

[0032] like Figure 3 As shown, the bent slot is divided into a radiating part Lf1 and a non-radiating part Lf2. The radiating part Lf1 cuts through the waveguide surface current to generate radiation, while the non-radiating part Lf2 is parallel to the length of the waveguide body and generates only a small amount of radiation because it is parallel to the surface current. The radiating part Lf1 is perpendicular to the inclined slot 3, creating a pair of orthogonal polarizations. The back-to-back waveguide wall height H1 is 0.25 times the wavelength, providing a 90° phase difference between the two polarizations, thus achieving circular polarization of the antenna. The waveguide uses center feeding. Since the slots on both sides of the waveguide are not symmetrically distributed, a groove 6 is used in the center of the waveguide to separate the electric fields on both sides, making the electric fields symmetrically distributed and thus not affecting the radiation performance.

[0033] The specific parameters for the embodiment are determined as follows:

[0034] In this embodiment, the tilt angle θ of the tilted slot can be adjusted according to the waveguide size. For example, if the waveguide width w1 needs to be reduced, the tilt angle θ can be reduced to adjust the tilted slot. The purpose is to make the amplitudes of the two orthogonal slots equal.

[0035] The lengths of the slanted and bent gaps must be 0.5 wavelengths. If the backrest width is too small to meet the 0.5 wavelength requirement for the gaps, the slanted gaps will extend to the side walls of the backrest. The height of the backrest waveguide wall is 1 / 4 wavelength, the height of the waveguide cross-section is less than 0.2 wavelengths, and the length of the waveguide cross-section is less than 0.7 wavelengths.

[0036] like Figures 1-4 The simulation example shown is for an 8-element circularly polarized waveguide standing wave antenna array with a center frequency of 10 GHz and a wavelength of 30 mm, arranged uniformly in the X-band. This antenna array has 8 elements on a single L-shaped waveguide, consisting of 8 bent slots on the bottom waveguide wall of the L-shaped waveguide and 8 inclined slots on the back waveguide wall of the L-shaped waveguide. The bottom width W of the L-shaped waveguide is 20 mm, the bottom height H2 is 5 mm, the width W1 of the back waveguide wall is 7.5 mm, and the height H1 of the back waveguide wall is 7.5 mm. The outer edge H3 of the symmetrical inclined slot is 2.5 mm, the inclination angle θ of the inclined slots on both sides of the back waveguide wall is 55°, the lengths of the two parts of the bent slot are Lf1 = 9.6 mm and Lf2 = 6.3 mm, and the slot width ws = 1 mm. The longitudinal spacing L between adjacent slots along the waveguide is 18.5 mm. The short road surface is 9.25 mm from the center of the last unit.

[0037] Figure 5 yes Figure 1 The antenna impedance bandwidth of the 8-element antenna embodiment varies with frequency. In the range of 8.9 to 10.5 GHz, S11 is less than -10 dB, and the impedance bandwidth is about 16%. Figure 6 The graph shows the axial ratio versus frequency for an 8-element antenna embodiment. In the range of 8.5 to 11 GHz, the axial ratio is less than 3 dB and the axial ratio bandwidth is approximately 25%. Figure 7 The image shows the radiation pattern at the center frequency and its cross-polarization in the antenna embodiment. The antenna gain is 14 dBi.

[0038] Example 2

[0039] Based on the antenna of Embodiment 1, this embodiment provides an antenna array.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A broadband circularly polarized waveguide slot antenna, comprising a waveguide body, two rows of backrest waveguide walls are arranged in parallel on the same A side of the waveguide body along the two extension directions of the center of the waveguide body; and the backrest waveguide walls in the same extension direction are arranged at intervals; characterized in that, Each backrest waveguide wall is provided with an inclined slot on the B side away from the A side; the A side is provided with a bending slot between two backrest waveguide walls in the same row, the bending slot includes a radiation part Lf1 and a non-radiation part Lf2; the bending slot and the inclined slot in the same row are arranged at intervals; The inclined directions of the two rows of inclined slots are consistent; the adjacent two bending slots in the two rows of bending slots are arranged in a 180° rotation symmetry with the Lf2 part end as the center; the centers of the two rows of bending slots and the centers of the two rows of inclined slots are in the same section of the L-shaped waveguide tube body and the backrest waveguide wall.

2. The wideband circularly polarized waveguide slot antenna according to claim 1, wherein, The bending slot includes the Lf2 part parallel to the length direction of the A side and the Lf1 part orthogonal to the inclined slot, wherein the Lf2 part does not cut the surface current and does not produce radiation, that is, the non-radiation part; the Lf1 part cuts the surface current and forms orthogonal polarization with the inclined slot, that is, the radiation part.

3. The wideband circularly polarized waveguide slot antenna of claim 1, wherein, The inclined slots in the same row are arranged at equal intervals.

4. The wideband circularly polarized waveguide slot antenna of claim 1, wherein, The waveguide slot antenna is center-fed, and a groove is arranged in the center of the waveguide tube body to separate the electric fields on both sides, so that the electric fields on both sides are symmetrically distributed.

5. The wideband circularly polarized waveguide slot antenna according to any one of claims 1 to 4, characterized in that, The inclined angle of the inclined slot is adjusted as needed.

6. The wideband circularly polarized waveguide slot antenna according to any one of claims 1 to 4, characterized in that, The length of the inclined slot and the bending slot is 0.5 wavelength.

7. The wideband circularly polarized waveguide slot antenna according to any one of claims 1 to 4, characterized in that, The height of the backrest waveguide wall is 1 / 4 wavelength, the height of the waveguide tube section is less than 0.2 wavelength, and the length of the waveguide tube section is less than 0.7 wavelength.

8. The wideband circularly polarized waveguide slot antenna according to any one of claims 1 to 4, characterized in that, The waveguide tube body and the backrest waveguide wall are made of metal or composite material plated with metal on the surface.

9. The wideband circularly polarized waveguide slot antenna according to any one of claims 1 to 4, characterized in that, The waveguide tube body and the backrest waveguide wall are integrally formed.

10. An antenna array comprising the waveguide slot antenna of any one of claims 1 to 8.

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