Broadband millimeter wave circularly polarized antenna array based on E-plane waveguide feed

Abstract

The invention discloses a broadband millimeter wave circularly polarized antenna array based on E-plane waveguide feed. The antenna array comprises a broadband linear polarization back cavity slot antenna sub-array and an E-plane waveguide multistage sequential rotation feed network. According to the invention, the plurality of broadband linearly polarized antenna sub-arrays are arranged according to a multi-stage sequential rotation mode, so that the axial ratio bandwidth performance of the circularly polarized antenna array is improved. Besides, the rectangular grooves are etched in the surface of the antenna array, so that non-ideal current distribution can be effectively suppressed, and the sidelobe level of the antenna array is suppressed while the gain of the antenna array is improved. The characteristic that the transverse size of the E-plane waveguide is compact is utilized, and the E-plane waveguide multi-stage sequential rotation feed network with a complex structure and the waveguide radiation units are placed in the same layer, so that a compact circularly polarized antenna array structure is realized. And the broadband circularly polarized antenna is realized by adjusting structural parameters of the phase shifter in the sequential rotation network. The circularly polarized antenna array provided by the invention has the performance advantages of single layer, compact structure and high gain while ensuring the broadband circular polarization performance, and is an excellent choice for millimeter wave wireless communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave and millimeter waves, and in particular to a broadband millimeter wave circularly polarized antenna array based on E-plane waveguide feeding. Background Art

[0002] Due to the abundant spectrum resources in the millimeter wave band, millimeter wave technology has garnered widespread attention in recent years, with applications such as millimeter wave vehicular radar, high-speed point-to-point wireless communications, synthetic aperture radar, and fifth-generation mobile communications. Millimeter wave antennas play a crucial role in millimeter wave wireless systems. Compared to traditional linearly polarized antennas, circularly polarized antennas offer superior performance in reducing polarization mismatch between transmit and receive antennas and suppressing multipath interference, making them widely used in various millimeter wave wireless systems. Given the high losses in the millimeter wave band, wideband, single-layer, high-gain, compact circularly polarized antenna arrays based on low-loss waveguide-like structures are a common requirement for various millimeter wave applications.

[0003] In recent years, domestic and foreign scholars have conducted extensive research on various types of high-performance, low-loss metal waveguide millimeter-wave circularly polarized antennas. At present, millimeter-wave all-metal circularly polarized antenna arrays (2D arrays) find it difficult to combine the two excellent characteristics of single layer and broadband (>35%). According to the feeding network form of the circularly polarized antenna array, the current circularly polarized antenna array can be divided into two categories. The first category is a circularly polarized antenna array based on an equal-amplitude and in-phase parallel feeding network. This type of antenna array requires that each radiating element can independently achieve circular polarization. In addition, the circular polarization axial ratio bandwidth of the antenna array will decrease as the array scale increases. The second category is a circularly polarized antenna array based on a single-stage / multi-stage sequential rotation network feeding. This type of antenna array can effectively improve the axial ratio performance of the circularly polarized antenna array. As the number of sequential rotation network stages increases, the performance of the circularly polarized antenna gradually improves. However, the single-stage / multi-stage sequential rotation feeding network has a complex structure and occupies a large size. Conventional technical solutions use a complex multi-layer process to place the sequential rotation network and antenna radiating elements separately. This not only increases the processing cost of the antenna, but also increases the overall cross-section of the circularly polarized antenna array. Summary of the Invention

[0004] The present invention aims to address the above-mentioned problems in the prior art by providing a broadband, single-layer millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding. While achieving a broadband (>35%) circularly polarized antenna array, the present invention also offers the technical advantages of a single layer, high gain, and compact structure.

[0005] The technical solution for achieving the purpose of the present invention is: a broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding, wherein the circularly polarized antenna array includes multiple linearly polarized cavity-backed slot antenna subarrays and an E-plane waveguide multi-stage sequential rotation feeding network. The multiple linearly polarized cavity-backed slot antenna subarrays are arranged in a multi-stage rotation sequence and fed by the E-plane waveguide multi-stage sequential rotation feeding network, thereby realizing broadband circularly polarized radiation.

[0006] Furthermore, the circularly polarized antenna array is a single-layer structure, and the E-plane waveguide multi-stage sequential rotation feeding network and the multiple linearly polarized cavity-backed slot antenna subarrays are located in the same layer.

[0007] Furthermore, when the plurality of linearly polarized cavity-backed slot antenna subarrays are rotated and arranged in a multi-stage sequence, a line connecting the centers of the physical structures of four adjacent linearly polarized cavity-backed slot antenna subarrays forms a parallelogram structure.

[0008] Furthermore, each of the linearly polarized cavity-backed slot antenna subarrays includes four E-plane waveguide-fed linearly polarized cavity-backed slot antenna units, and a one-to-four parallel-feed feeding network connected to the four E-plane waveguide-fed linearly polarized cavity-backed slot antenna units; the top projection of the linearly polarized cavity-backed slot antenna units is a rectangular structure, and the four linearly polarized cavity-backed slot antenna units are distributed in a 2×2 array and present a completely axisymmetric structure; in each linearly polarized cavity-backed slot antenna subarray, three rectangular grooves are etched along the wide side direction of the rectangular structure of the top projection of all linearly polarized cavity-backed slot antenna units, including a first rectangular groove located between two columns of linearly polarized cavity-backed slot antenna units, and a second rectangular groove and a third rectangular groove located on the outside of the two columns of linearly polarized cavity-backed slot antenna units, respectively.

[0009] Furthermore, the depth of the rectangular groove is about 0.25λ0, where λ0 is the wavelength of air at the center frequency of the working frequency band.

[0010] Furthermore, each of the E-plane waveguide-fed linearly polarized cavity-backed radiation slot antenna units includes a stepped radiation cavity with an open terminal and a metal ridge, the stepped radiation cavity with an open terminal includes a metal back cavity and a stepped radiation slot arranged at the radiation aperture of the metal back cavity, and the metal ridge is arranged in the middle position of the bottom of the metal back cavity.

[0011] Furthermore, the four feed output ports of the one-to-four parallel feed structure feed network are respectively located at the wide side of the metal back cavity of each linear polarization back cavity radiation slot antenna unit in the linear polarization back cavity slot antenna subarray, that is, the wide side of the rectangular structure.

[0012] Furthermore, the circularly polarized antenna array includes 2 N ×2 N Linearly polarized cavity-backed radiation slot antenna units form 2 N-1 ×2N-1 Linearly polarized cavity-backed slot antenna subarrays, N≥2.

[0013] Furthermore, the E-plane waveguide multi-stage sequential rotation feeding network includes an N-1 stage sequential rotation feeding network; the N-1 stage sequential rotation feeding network includes: 2 0 ×2 0 N-1th level sequential rotating feed network, 2 1 ×2 1 N-2th level sequential rotating feed network, 2 2 ×2 2 N-3th level sequential rotating feed network, ..., 2 N-1 ×2 N-1 A first-level sequential rotating feed network;

[0014] All N-1th level sequential rotary feed networks consist of one input port and 2 1 ×2 1 Output ports, all N-2 level sequential rotary feed networks include 2 1 ×2 1 input ports and 2 2 ×2 2 Output ports, and so on, ..., all first-level sequential rotary feed networks include 2 N-2 ×2 N-2 input ports and 2 N-1 ×2 N-1 output ports; among them, the input ports of all N-1th level sequential rotation feeding networks are used as the input ports of the entire antenna array, and then the output ports and input ports are connected in the order of N-1th level sequential rotation feeding network, N-2th level sequential rotation feeding network, N-3th level sequential rotation feeding network, ..., 1st level sequential rotation feeding network. Finally, the 2nd level of all 1st level sequential rotation feeding networks are connected. N-1 ×2 N-1 The output ports are connected to 2 N-1 ×2 N-1 The feeding input port of the feeding network of the one-to-four parallel feeding structure of the linearly polarized cavity-backed slot antenna subarray.

[0015] Furthermore, each level of the E-plane waveguide multi-level sequential rotation feeding network is realized by a plurality of E-plane waveguide unequal width and unequal length phase shifters and a plurality of E-plane waveguide 1-to-2 power splitters.

[0016] Compared with the prior art, the present invention has the following significant advantages:

[0017] (1) Due to the complex structure and large size of the sequential rotation network, existing millimeter-wave sequential rotation feeding circularly polarized antenna array solutions usually adopt a multi-layer structure to place the complex sequential rotation feeding network and antenna radiating units separately. This not only increases the antenna processing cost, but also increases the cross-section of the antenna array. The present invention arranges multiple antenna sub-arrays in a multi-level sequential rotation. Taking advantage of the compact lateral size of the E-plane waveguide, a compact multi-level E-plane waveguide sequential rotation feeding network is designed, and the multi-level sequential rotation network and the antenna radiating units are placed in the same layer, thereby realizing a compact single-layer circularly polarized antenna array.

[0018] 2) The present invention etches rectangular grooves between the different radiating elements of the antenna subarray. These grooves effectively suppress non-ideal anti-phase surface current distribution and serve as secondary radiation sources to further radiate surface wave energy, effectively increasing the gain of the antenna subarrays and the entire circularly polarized antenna array while suppressing the antenna array sidelobe level.

[0019] 3) In order to achieve good circularly polarized radiation performance over a wide frequency band, both the cavity-backed slot antenna unit and the multi-stage E-plane waveguide sequential rotation network must have broadband characteristics. The present invention loads a stepped radiation cavity and a metal ridge on the cavity-backed slot antenna unit, which can effectively increase the gain of the antenna unit and improve the impedance matching performance of the antenna unit. At the same time, a broadband, compact E-plane waveguide multi-stage sequential rotation network is designed using broadband E-plane waveguide unequal width and length phase shifters, which can provide the required amplitude and phase distribution within a wide frequency band, thereby realizing a broadband circularly polarized antenna array.

[0020] 4) The present invention rotates multiple broadband linearly polarized subarrays in a multi-level sequence and feeds them through a multi-level E-plane waveguide sequential rotation network, realizing a broadband, single-layer millimeter-wave circularly polarized antenna array. Compared with traditional multi-layer all-metal circularly polarized antenna arrays, the circularly polarized antenna array proposed in the design example of the present invention achieves an impedance bandwidth of 37.62% (25.9-37.9 GHz) and a 3dB axial ratio bandwidth of 43.75% (25-39 GHz). It also has the performance advantages of a single layer, compact structure, high gain (24.9 dBic), and high polarization purity (1dB axial ratio bandwidth can reach 33.85%, covering 27-38 GHz), making it an excellent choice for millimeter-wave wireless communications.

[0021] The present invention is described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG is a structural diagram of a broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding in one embodiment, wherein Figure 1 (a) is the 3D structure diagram of the antenna array. Figure 1 (b) is a top view of the antenna array. Figure 1 (c) is a cross-sectional view of the antenna array cut along the middle.

[0023] Figure 2 Schematic diagram of the design evolution of the cavity-backed radiation slot antenna unit in one embodiment, wherein Figure 2 (a) is the initial radiation slot antenna unit, Figure 2 (b) in the figure is a radiation slot antenna unit loaded with a stepped radiation cavity and a metal ridge.

[0024] Figure 3 Schematic diagram of reflection coefficient and gain changes corresponding to the design evolution of cavity-backed radiation slot antenna unit in one embodiment, where Figure 3 (a) is a schematic diagram of the reflection coefficient. Figure 3 (b) in the figure is a schematic diagram of gain change.

[0025] Figure 4 FIG is a schematic diagram of a broadband linear polarization subarray structure in one embodiment, wherein Figure 4 (a) to (c) are the top view, side view, and three-dimensional structure schematic diagram of the antenna subarray, respectively.

[0026] Figure 5 Schematic diagram of the changes in the electric field and surface current distribution of the antenna aperture surface before and after the rectangular groove is loaded on the antenna subarray in one embodiment, wherein Figure 5 (a)-(c) are the electric field distribution diagram (top view), surface current distribution diagram (side view), and surface current distribution diagram (top view) of the antenna subarray radiation aperture when no rectangular groove is loaded. Figure 5 (d)-(f) are the electric field distribution diagram of the antenna subarray radiation aperture (top view), surface current distribution diagram (side view), and surface current distribution diagram (top view) when the rectangular groove is loaded.

[0027] Figure 6 FIG. 1 is a schematic diagram showing the change of antenna side lobes before and after the rectangular groove is loaded on the antenna subarray in one embodiment, wherein Figure 6 (a) is the comparison of the antenna radiation pattern of the antenna subarray before and after the rectangular groove is loaded at 34GHz. Figure 6 (b) is a schematic diagram of the change of antenna side lobes at different frequencies before and after the rectangular groove is loaded into the antenna subarray.

[0028] Figure 7 A perspective view of a broadband circularly polarized antenna array according to an embodiment of the present invention is shown.

[0029] Figure 8 : is a local aperture surface electric field distribution diagram of a broadband circularly polarized antenna array in one embodiment, wherein (a) in 8 is a local aperture surface electric field distribution diagram at t=0, Figure 8(b) is the local aperture electric field distribution diagram when t = T / 4, where T represents the electromagnetic wave period corresponding to the antenna's working center frequency.

[0030] Figure 9 FIG1 is a schematic diagram of the antenna pattern and gain changes of a broadband circularly polarized antenna array before and after loading a rectangular groove in one embodiment, wherein Figure 9 (a) is the antenna pattern, Figure 9 (b) in the figure is a schematic diagram of gain change.

[0031] Figure 10 Figure 1 is a schematic diagram of the first-stage E-plane waveguide sequential rotation network structure and the corresponding simulation results in one embodiment, wherein Figure 10 (a) is a schematic diagram of the three-dimensional structure of the first-level E-plane waveguide sequential rotation network. Figure 10 (b) is a top view of the first-level E-plane waveguide sequential rotation network. Figure 10 (c) is the S parameter result of the first-level E-plane waveguide sequential rotation network simulation. Figure 10 (d) in the figure is the simulated phase distribution result of the first-level E-plane waveguide sequential rotation network.

[0032] Figure 11 Schematic diagram of the second-stage E-plane waveguide sequential rotation network structure and corresponding simulation results in one embodiment. Figure 11 (a) is a schematic diagram of the three-dimensional structure of the second-level E-plane waveguide sequential rotation network. Figure 11 (b) is a top view of the second-level E-plane waveguide sequential rotation network. Figure 11 (c) is the S parameter result of the second-level E-plane waveguide sequential rotation network simulation. Figure 11 (d) in the figure is the simulated phase distribution result of the second-level E-plane waveguide sequential rotation network.

[0033] Figure 12 The figure is a schematic diagram comparing the axial ratio performance of circularly polarized arrays under single-stage sequential rotation network and two-stage sequential rotation network feeding modes in one embodiment.

[0034] Figure 13 The broadband circularly polarized antenna array is measured and simulated in one embodiment. 11 |Curve chart.

[0035] Figure 14 is the radiation pattern of a broadband circularly polarized antenna array in one embodiment (35 GHz, xoz plane yoz plane), Figure 14 (a) is the antenna array radiation pattern (35GHz, xoz plane), Figure 14 (b) in the figure is the radiation pattern of the antenna array (35GHz, yoz plane).

[0036] Figure 15 FIG. 4 is a graph showing gain and axial ratio of a broadband circularly polarized antenna array in one embodiment. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0038] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0039] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] In one embodiment, combined Figure 1 , provides a broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding, the circularly polarized antenna array includes multiple linearly polarized back-cavity slot antenna subarrays 4 and an E-plane waveguide multi-stage sequential rotation feeding network 5, the multiple linearly polarized back-cavity slot antenna subarrays 4 are arranged in a multi-stage rotation sequence and fed by the E-plane waveguide multi-stage sequential rotation feeding network, thereby realizing broadband circularly polarized radiation.

[0041] Furthermore, in one embodiment, the circularly polarized antenna array is a single-layer structure, and the E-plane waveguide multi-stage sequential rotation feeding network 5 and the multiple linearly polarized cavity-backed slot antenna sub-arrays 4 are located in the same layer.

[0042] Due to the complex structure and large size of the sequential rotation network, existing millimeter-wave sequential rotation feed circularly polarized antenna array solutions typically use a multi-layer structure to separately place the complex sequential rotation feed network and antenna radiating elements. This not only increases the antenna processing cost but also increases the cross-section of the antenna array. The present invention arranges multiple antenna subarrays in a multi-level sequential rotation. Taking advantage of the compact lateral dimensions of the E-plane waveguide, a compact multi-level E-plane waveguide sequential rotation feed network is designed. The multi-level sequential rotation network and the antenna radiating elements are placed in the same layer, thus realizing a compact single-layer circularly polarized antenna array.

[0043] Furthermore, in one embodiment, when the plurality of linearly polarized cavity-backed slot antenna subarrays 4 are rotated and arranged in a multi-stage sequence, a line connecting the centers of the physical structures of four adjacent linearly polarized cavity-backed slot antenna subarrays 4 forms a parallelogram structure.

[0044] By adopting the solution of this embodiment, the structure of the multi-stage E-plane waveguide sequential rotation feeding network is made more compact.

[0045] It should be noted here that the sequential rotation mode and arrangement mode can be adaptively adjusted according to the requirements of structural compactness to form other structures such as square structures.

[0046] Furthermore, in one embodiment, in combination Figure 4 Each of the linearly polarized cavity-backed slot antenna subarrays includes four E-plane waveguide-fed linearly polarized cavity-backed slot antenna units 1, and a one-to-four parallel-feed feeding network connected to the four E-plane waveguide-fed linearly polarized cavity-backed slot antenna units 1; the top projection of the linearly polarized cavity-backed slot antenna unit 1 is a rectangular structure, and the four linearly polarized cavity-backed slot antenna units 1 are distributed in a 2×2 array and present a completely axisymmetric structure; in each linearly polarized cavity-backed slot antenna subarray, three rectangular grooves 3 are etched along the wide side direction of the rectangular structure of the top projection of all linearly polarized cavity-backed slot antenna units 1, including a first rectangular groove located between two columns of linearly polarized cavity-backed slot antenna units 1, and a second rectangular groove and a third rectangular groove located on the outside of the two columns of linearly polarized cavity-backed slot antenna units 1, respectively.

[0047] Further preferably, in some embodiments, the depth of the rectangular groove 3 is about 0.25λ0, where λ0 is the wavelength of air at the center frequency of the working frequency band.

[0048] Further preferably, in some embodiments, combined Figure 2 Each of the E-plane waveguide-fed linearly polarized cavity-backed radiation slot antenna units 1 includes an open-ended stepped radiation cavity 6 and a metal ridge 2. The open-ended stepped radiation cavity 6 includes a metal back cavity and a stepped radiation slot arranged at the radiation aperture of the metal back cavity. The metal ridge 2 is arranged in the middle of the bottom of the metal back cavity.

[0049] here, Figure 2-Figure 3 The present invention shows a schematic diagram of the design and research of the cavity-backed slot antenna unit. First, the cavity-backed slot antenna unit (Ant1) based on E-plane waveguide feeding is used. The operating frequency band of the antenna unit is adjusted by adjusting the metal cavity size (wide side length w and narrow side length l). In order to improve the impedance matching performance and antenna gain of the antenna unit within the operating frequency band, the present invention adds a metal ridge at the bottom of the metal cavity and introduces a stepped radiation slot at the radiation aperture (see Figure 2 ). It effectively improves the impedance matching performance of the cavity-backed slot antenna unit (38.89%, 26.1-38.7GHz) and increases the antenna unit gain (the increase exceeds 1dB at most operating frequencies, see Figure 3 ).

[0050] Further preferably, in some embodiments, the four feed output ports of the feeding network of the one-to-four parallel feed structure are respectively located at the wide side position of the metal back cavity of each linearly polarized back cavity radiation slot antenna unit 1 in the linearly polarized back cavity slot antenna subarray, that is, the wide side position of the rectangular structure.

[0051] Preferably, in some embodiments, the four feed output ports are respectively located at four mutually adjacent broadside positions of the metal back cavity of each linearly polarized back cavity radiation slot antenna unit (1), thereby further realizing a compact structural design.

[0052] here, Figure 4-Figure 6 The design principle of broadband linear polarization cavity-backed slot antenna subarray involved in this invention is demonstrated. Figure 4 The antenna subarray shown consists of four cavity-backed slot antenna elements and a compact parallel feed network. The antenna subarray is fed by an E-plane waveguide with rectangular grooves etched into the subarray surface. Because the E-plane waveguide 1-to-2 power splitter naturally exhibits phase reversal, the upper and lower cavity-backed feed points are symmetrically positioned about the center, resulting in a more compact feeding structure. Figure 5 The changes in the electric field and surface current distribution before and after the rectangular grooves are loaded on the surface of the antenna subarray are shown. When the rectangular grooves are not etched on the surface of the antenna subarray, there is an inverted surface current distribution on the radiation aperture surface, which reduces the antenna gain and leads to higher antenna side lobes. To solve the above problems, the present invention etches rectangular grooves on the surface of the adjacent back cavity radiation slots of the antenna subarray. The introduced rectangular grooves can effectively suppress the inverted surface current distribution, and the grooves themselves can act as a secondary radiation source to radiate the metal surface wave energy (see Figure 5). The depth of the groove will affect the performance of the designed antenna subarray. In this embodiment, the groove depth is about 0.25λ0 (λ0 is the air wavelength at the center frequency of the working frequency band). At this time, a groove with a depth of one quarter wavelength can produce an electric field distribution on the surface of the radiation aperture that is in phase with the four back-cavity radiation slot antenna units. At this time, the rectangular groove can be used as a secondary radiation source to effectively radiate the surface wave energy. Compared with the antenna subarray without etching the rectangular groove, the introduction of the rectangular groove can effectively improve the gain of the antenna subarray while suppressing the side lobes of the antenna array (see Figure 6 ).

[0053] Figure 7-Figure 9 The design process of circularly polarized array antenna array is demonstrated. Figure 7 This is a three-dimensional top view (transmission perspective) of the millimeter wave circularly polarized antenna array. Multiple antenna sub-arrays are arranged in a sequential rotation pattern, and multiple groups of rectangular grooves are also etched on the surface of the antenna sub-array. It can be seen from the electric field distribution of the circularly polarized antenna array (see Figure 8 ), the rectangular grooves on the circularly polarized antenna array have a strong electric field strength, which can be used as a secondary radiation source to radiate the surface wave energy on the metal surface. Compared with the circularly polarized antenna array without rectangular grooves, the rectangular grooves introduced in the present invention can effectively improve the gain of the entire circularly polarized antenna array and suppress the grating lobes of the circularly polarized antenna array (see Figure 9 ).

[0054] Furthermore, in one embodiment, the broadband end-fire circularly polarized antenna unit proposed in the present invention can be easily expanded to 2 N ×2 N (N≥2) circularly polarized antenna array, that is, the circularly polarized antenna array includes 2 N ×2 N Linear polarization cavity-backed radiation slot antenna unit (1), forming 2 N-1 ×2 N-1 Linearly polarized cavity-backed slot antenna subarrays, N≥2.

[0055] Further preferably, in some embodiments, the E-plane waveguide multi-stage sequential rotation feeding network 5 includes an N-1-stage sequential rotation feeding network; the E-plane waveguide multi-stage sequential rotation feeding network 5 includes an N-1-stage sequential rotation feeding network; the N-1-stage sequential rotation feeding network includes: 2 0 ×2 0 N-1th level sequential rotating feed network, 2 1 ×2 1 N-2th level sequential rotating feed network, 2 2 ×2 2 N-3th level sequential rotating feed network, ..., 2 N-1 ×2 N-1A first-level sequential rotating feed network;

[0056] All N-1th level sequential rotary feed networks consist of one input port and 2 1 ×2 1 Output ports, all N-2 level sequential rotary feed networks include 2 1 ×2 1 input ports and 2 2 ×2 2 Output ports, and so on, ..., all first-level sequential rotary feed networks include 2 N-2 ×2 N-2 input ports and 2 N-1 ×2 N-1 output ports; among them, the input ports of all N-1th level sequential rotation feeding networks are used as the input ports of the entire antenna array, and then the output ports and input ports are connected in the order of N-1th level sequential rotation feeding network, N-2th level sequential rotation feeding network, N-3th level sequential rotation feeding network, ..., 1st level sequential rotation feeding network. Finally, the 2nd level of all 1st level sequential rotation feeding networks are connected. N-1 ×2 N-1 The output ports are connected to 2 N-1 ×2 N-1 The feeding input port of the feeding network of the one-to-four parallel feeding structure of the linearly polarized cavity-backed slot antenna subarray.

[0057] Here, the antenna array is fed by an N-1-level E-surface waveguide sequential rotation feeding network. N-1 ×2 N-1 Output ports and 2 N-1 ×2 N-1 The input ports of the cavity-backed radiation slot antenna subarrays are connected.

[0058] Here, the E-plane waveguide multi-stage sequential rotation feeding network designed by the present invention can further realize a compact single-layer circularly polarized antenna array structure.

[0059] Further preferably, in some embodiments, each level of the sequential rotation feeding network in the E-plane waveguide multi-level sequential rotation feeding network is realized by a plurality of E-plane waveguide unequal width and unequal length phase shifters and a plurality of E-plane waveguide 1-to-2 power splitters.

[0060] Here, since the E-plane waveguide 1-to-2 power splitter has a natural anti-phase characteristic, a combination of a 90° phase shifter and a 1-to-2 anti-phase power splitter is required to achieve a sequential rotation phase distribution of 0°, 90°, 180°, and 360°, thereby further realizing a compact E-plane waveguide sequential rotation network design.

[0061] Here, preferably, each sequential rotation feeding network in each level of sequential rotation feeding network includes 2 E-plane waveguide unequal width and unequal length phase shifters and 3 E-plane waveguide 1-to-2 power splitters (each level of sequential rotation feeding network includes multiple sequential rotation feeding networks, and each sequential rotation feeding network has one input and four outputs).

[0062] As a specific example, the present invention is further verified and explained in one of the embodiments.

[0063] In order to verify the authenticity and reliability of the E-plane waveguide circularly polarized antenna array proposed in the present invention, an 8×8 scale E-plane waveguide circularly polarized antenna array was produced in this embodiment for verification. The specific structure is as follows: Figure 1 shown.

[0064] The multi-stage sequential rotation network in this embodiment is a two-stage E-plane waveguide sequential rotation network (N=3), and its feeding network structure and related simulation design results are shown in FIG. Figure 10-11 As shown. Each level of the E-plane waveguide sequential rotation network is composed of a broadband E-plane waveguide unequal width and unequal length phase shifter and an E-plane waveguide 1-to-2 power divider. By adjusting the relevant structural parameters of the E-plane waveguide phase shifter, a good sequential rotation phase distribution (0°, 90°, 180°, 270°) can be achieved in a wide frequency band. Compared with the circularly polarized antenna array fed by a single-stage sequential rotation network, the multi-stage sequential rotation feeding circularly polarized antenna array proposed in the present invention can significantly broaden the axial ratio bandwidth and improve the circular polarization purity (the axial ratio of most frequency points in the working frequency band is <1dB, see Figure 12 ).

[0065] Figures 13 to 15 The simulation and measured performance parameters of the E-plane waveguide circularly polarized antenna array, including |S11|, antenna radiation pattern, circular polarization gain, and axial ratio, are presented. Figure 13-15 It can be seen that the simulation results of the circularly polarized antenna are in good agreement with the measured results. The measured results show that the |S 11 The -10dB impedance bandwidth is 37.62% (25.9-37.9GHz), and the 3dB axial ratio bandwidth is 43.75% (25-39GHz). Because the circularly polarized antenna array described in this invention utilizes a multi-stage sequential rotation network feed, it achieves high circular polarization purity. The axial ratio at most frequencies within the operating band can be less than 1dB (the 1dB axial ratio bandwidth is 33.85% (27-38GHz)).

[0066] In summary, the E-plane waveguide circularly polarized antenna array proposed in the present invention can not only achieve broadband circularly polarized radiation, but also has performance advantages such as single-layer, compact array structure, high gain, and high polarization purity. It is an excellent choice for millimeter-wave wireless communications.

[0067] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding, characterized in that: The circularly polarized antenna array comprises a plurality of linearly polarized cavity-backed slot antenna subarrays (4) and an E-plane waveguide multi-stage sequential rotation feeding network (5); the plurality of linearly polarized cavity-backed slot antenna subarrays (4) are arranged in a multi-stage sequential rotation and fed by the E-plane waveguide multi-stage sequential rotation feeding network, thereby achieving broadband circularly polarized radiation.

2. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 1, characterized in that: The circularly polarized antenna array is a single-layer structure, and the E-plane waveguide multi-stage sequential rotation feeding network (5) and the plurality of linearly polarized cavity-backed slot antenna subarrays (4) are located in the same layer.

3. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 1, characterized in that: When a plurality of linearly polarized cavity-backed slot antenna subarrays (4) are arranged in a rotational manner in a multi-stage sequence, a center line connecting the physical structures of four adjacent linearly polarized cavity-backed slot antenna subarrays (4) forms a parallelogram structure.

4. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 1, characterized in that: Each of the linearly polarized cavity-backed slot antenna subarrays comprises four E-surface waveguide-fed linearly polarized cavity-backed slot antenna units (1), and a one-to-four parallel-feed feeding network connected to the four E-surface waveguide-fed linearly polarized cavity-backed slot antenna units (1); the top projection of the linearly polarized cavity-backed slot antenna units (1) is a rectangular structure, and the four linearly polarized cavity-backed slot antenna units (1) are distributed in a 2×2 array and present a completely axisymmetric structure; in each linearly polarized cavity-backed slot antenna subarray, three rectangular grooves (3) are etched along the wide side direction of the rectangular structure of the top projection of all the linearly polarized cavity-backed slot antenna units (1), including a first rectangular groove located between two columns of the linearly polarized cavity-backed slot antenna units (1), and a second rectangular groove and a third rectangular groove located outside the two columns of the linearly polarized cavity-backed slot antenna units (1).

5. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 4, characterized in that: The depth of the rectangular groove (3) is about 0.25λ0, where λ0 is the wavelength of air at the center frequency of the working frequency band.

6. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 4, characterized in that: Each of the E-plane waveguide-fed linearly polarized cavity-backed radiation slot antenna units (1) comprises a terminal-open stepped radiation cavity (6) and a metal ridge (2); the terminal-open stepped radiation cavity (6) comprises a metal back cavity and a stepped radiation slot arranged at a radiation aperture of the metal back cavity; the metal ridge (2) is arranged at the bottom middle position of the metal back cavity.

7. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 6, characterized in that: The four feed output ports of the one-to-four parallel feed structure feed network are respectively located at the wide side position of the metal back cavity of each linear polarization back cavity radiation slot antenna unit (1) in the linear polarization back cavity slot antenna subarray, that is, the wide side position of the rectangular structure.

8. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 4, characterized in that: The circularly polarized antenna array includes 2 N ×2 N Linear polarization cavity-backed radiation slot antenna unit (1), forming 2 N-1 ×2 N-1 Linearly polarized cavity-backed slot antenna subarrays, N≥2.

9. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 8, characterized in that: The E-plane waveguide multi-stage sequential rotation feeding network (5) includes an N-1-stage sequential rotation feeding network; the N-1-stage sequential rotation feeding network includes: 2 0 ×2 0 N-1th level sequential rotating feed network, 2 1 ×2 1 N-2th level sequential rotating feed network, 2 2 ×2 2 N-3th level sequential rotating feed network, ..., 2 N-1 ×2 N-1 A first-level sequential rotating feed network; All N-1th level sequential rotary feed networks consist of one input port and 2 1 ×2 1 Output ports, all N-2 level sequential rotary feed networks include 2 1 ×2 1 input ports and 2 2 ×2 2 Output ports, and so on, ..., all first-level sequential rotary feed networks include 2 N-2 ×2 N-2 input ports and 2 N-1 ×2 N-1 output ports; among them, the input ports of all N-1th level sequential rotation feeding networks are used as the input ports of the entire antenna array, and then the output ports and input ports are connected in the order of N-1th level sequential rotation feeding network, N-2th level sequential rotation feeding network, N-3th level sequential rotation feeding network, ..., 1st level sequential rotation feeding network. Finally, the 2nd level of all 1st level sequential rotation feeding networks are connected. N-1 ×2 N-1 The output ports are connected to 2 N-1 ×2 N-1 The feeding input port of the feeding network of the one-to-four parallel feeding structure of the linearly polarized cavity-backed slot antenna subarray.

10. The broadband millimeter-wave circularly polarized antenna array based on E-plane waveguide feeding according to claim 9, characterized in that: Each level of the sequential rotation feeding network in the E-plane waveguide multi-level sequential rotation feeding network (5) is realized by a plurality of E-plane waveguide unequal width and unequal length phase shifters and a plurality of E-plane waveguide 1-to-2 power splitters.

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