A broadband stepped-membrane waveguide dual-circular polarizer

Abstract

The application discloses a broadband stepped film waveguide dual circular polarizer, and belongs to the technical field of microwave and millimeter wave. The device comprises a left-handed circular polarization feed waveguide, a right-handed circular polarization feed waveguide, two 90-degree waveguide bends, a radiation waveguide and a stepped film. The two feed waveguides are connected to the radiation waveguide through the 90-degree waveguide bends. The radiation waveguide is composed of a square waveguide and a cross-shaped waveguide, and is divided into an input section, a polarization separation / forming section and an output section which are connected in sequence. The input section is divided into left and right cavities by a waveguide wall. The polarization separation / forming section is provided with the stepped film. The left and right cavity sections are completely fused in the output section. The application adjusts waveguide dispersion, significantly expands the interval between the working mode and the high-order mode, and realizes the broadband working of the stepped film waveguide dual circular polarizer. At this time, the polarization separation / forming section can realize a 90-degree phase difference in a short distance, which is beneficial to reducing the transmission loss of the device and improving the compactness of the device.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave and millimeter wave technology, and particularly relates to a wideband stepped diaphragm waveguide dual circular polarizer. BACKGROUND

[0002] With the development of satellite communication and remote sensing technology, it is necessary to track and measure space targets under different polarization modes and weather conditions. Circularly polarized waves have the advantages of anti-cloud and rain attenuation, anti-multipath fading, and the ability to eliminate the influence of polarization distortion caused by ionospheric Faraday rotation effect. Therefore, circularly polarized antennas are increasingly valued in the fields of communication, radar, electronic countermeasures, remote sensing, astronomy, and television broadcasting.

[0003] A diaphragm type dual circular polarizer can produce circularly polarized waves with different spin directions by using different feed channels, and realize simultaneous transmission and reception of beams, which has a wide application in the fields of communication, guidance, and electronic reconnaissance. The traditional stepped diaphragm waveguide dual circular polarizer mainly consists of a radiation waveguide, a dual circular polarized stepped diaphragm waveguide, a left-handed circular polarized feed waveguide, and a right-handed circular polarized feed waveguide. Due to waveguide dispersion, the diaphragm type dual circular polarizer is prone to resonance in a wide frequency band, resulting in a sharp decline in electrical performance. Therefore, the traditional stepped diaphragm waveguide dual circular polarizer is difficult to achieve wideband operation. With the development of millimeter wave application technology, such as high-resolution imaging technology, there is a demand for wider frequency band operation of antenna systems. Developing wideband waveguide dual circular polarizer technology and eliminating the resonance phenomenon of traditional stepped diaphragm waveguide dual circular polarizers is of great significance to reducing the number of antennas, reducing costs, and promoting the development of millimeter wave communication and remote sensing technology.

[0004] The patent "Compact wedge-shaped tapered waveguide cavity circular polarizer" (CN103730737B) adopts a wedge-shaped tapered waveguide cavity to design a compact circular polarizer. The input and output ends of the circular polarizer are square waveguides, so additional square-to-rectangular waveguide conversion is required when feeding, which is inconvenient to use. At the same time, the input end size is larger than the output port, which will cause the antenna element spacing to be too large when forming an array antenna, thereby being not conducive to controlling the grating lobes.

[0005] The patent "Wideband stepped diaphragm waveguide dual circular polarizer" (application number 201811614820) eliminates the resonance phenomenon existing in the traditional stepped diaphragm dual circular polarizer by setting a waveguide ridge with a width greater than the diaphragm on the inner waveguide wall of the square waveguide. However, there are continuous inclined waveguide transition ridges in the dual circular polarizer, and they need to maintain a stable positional relationship with the stepped diaphragm, so the processing and installation precision requirements are high, which makes it difficult to guarantee the performance of the device when used in the high frequency band of millimeter waves. At the same time, the realization of high-precision technology will also lead to high cost of the device. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application aims to eliminate the resonance phenomenon caused by the emergence of high-order modes in the traditional stepped iris waveguide dual circular polarizer while maintaining the compact structure, stable performance and easy implementation of the traditional iris waveguide dual circular polarizer, and to realize wideband operation of the iris waveguide dual circular polarizer.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A wideband stepped iris waveguide dual circular polarizer, characterized in that the wideband stepped iris waveguide dual circular polarizer is a left-right symmetrical structure, comprising a left-handed circular polarization feed waveguide, a right-handed circular polarization feed waveguide, two 90° waveguide bends, a radiation waveguide and a stepped iris.

[0009] The left-handed circular polarization feed waveguide and the right-handed circular polarization feed waveguide are rectangular stepped waveguides with the same structure and symmetrical arrangement, and are connected to the radiation waveguide through a 90° waveguide bend respectively, and the cavity part as a whole is in T shape. The rectangular stepped waveguide is an impedance matching waveguide, which realizes the matching between the standard waveguides and the radiation waveguide.

[0010] The radiation waveguide is composed of a square waveguide and at least one cross-shaped waveguide superimposed, and the central axis of the square waveguide and the cross-shaped waveguide coincide, and the edges of the square waveguide are parallel to the arms of the cross-shaped waveguide; the radiation waveguide is divided into an input section, a polarization separation / forming section and an output section connected in turn; wherein the middle part of the input section is provided with a waveguide wall to divide it into left and right two-part cavities, and is respectively communicated with two 90° waveguide bends; the polarization separation / forming section is provided with a stepped iris with uniform thickness, which gradually decreases in height along the direction of electromagnetic wave propagation, and when reaching the output section, the left and right two-part cavities are completely fused.

[0011] Further, the cross-shaped waveguide with the longest arm has an arm length equal to the width of the 90° waveguide bend.

[0012] Further, the cross section of the radiation waveguide is a symmetrical polygon, and the length of each side is not less than 1mm.

[0013] Further, the inner wall of the radiation waveguide is rounded at right angles to facilitate processing.

[0014] Further, the thickness of the stepped iris is greater than 0.2mm and less than 1mm to reduce the processing difficulty and reduce the standing wave.

[0015] Further, the wideband stepped iris waveguide dual circular polarizer is processed by a conventional numerical control lathe, or is realized by 3D printing and injection molding processing methods.

[0016] The working principle of the application is as follows: electromagnetic waves are fed from the standard waveguide port of the left-handed circularly polarized feed waveguide or the right-handed circularly polarized feed waveguide, and enter the radiation waveguide through the 90° waveguide elbow. The input section of the radiation waveguide is arranged to facilitate processing and assembly. In the polarization separation / forming section, due to the presence of the stepped film sheet, the entering linearly polarized wave is decomposed into a pair of equal-amplitude orthogonal linearly polarized waves, and the formed orthogonal linearly polarized waves have different propagation constants. After the beam propagates through the stepped film sheet, the phase difference reaches 90 degrees, realizing the conversion of different linearly polarized waves into circularly polarized waves. Due to the difference of the feed port, the phase difference of the beam in the vertical direction and the horizontal direction exists in advance or lag, thereby forming corresponding left-handed or right-handed circularly polarized waves at the output port. Different from the previous design, the circularly polarized output waveguide proposed in the application can adjust the waveguide dispersion by increasing the number of radiation waveguide boundaries, greatly expand the interval between the working mode and the adjacent high-order mode. At the same time, by adjusting the size of the stepped film sheet, the mode interval between the working mode and the adjacent high-order mode is further expanded, so that the proposed dual circular polarizer can work in a single mode in a wide frequency band, solving the problem of resonance caused by the existence of high-order modes in the traditional film sheet circular polarizer, and realizing the wideband working of the stepped film waveguide dual circular polarizer.

[0017] The technical scheme of the application has the following advantages:

[0018] 1. The application significantly expands the interval between the working mode and the high-order mode by adjusting the waveguide dispersion, thereby solving the problem of resonance caused by the existence of high-order modes in the traditional film sheet circular polarizer, and realizing the wideband working of the stepped film waveguide dual circular polarizer.

[0019] 2. Due to the existence of the cross waveguide, the difference between the propagation constants of the electromagnetic wave in different polarization directions after entering the polarization separation / forming section of the radiation waveguide is large, and the 90° phase difference can be realized in a short distance, which is beneficial to reducing the transmission loss of the device and improving the compactness of the device.

[0020] 3. The output port of the application is composed of square waveguides and cross waveguides, which has high similarity with standard circular waveguides and square waveguides, and is convenient for connecting with the common interface of the dual circular polarized antenna. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic diagram of the cavity part of the embodiment of the application;

[0022] Figure 2 is a sectional view of the cavity part of the embodiment of the application;

[0023] Figure 3 is a schematic diagram of the overall structure of the embodiment of the application;

[0024] Figure 4is a schematic diagram of a radiation waveguide cavity part of an embodiment of the present application

[0025] Figure 5 is a schematic diagram of a radiation waveguide composed of a square waveguide and a cross waveguide according to the present application;

[0026] Figure 6 is a port voltage standing wave ratio result diagram of an embodiment of the present application;

[0027] Figure 7 is a port isolation result diagram of an embodiment of the present application;

[0028] Figure 8 is an axial ratio result diagram of an embodiment of the present application.

[0029] Legend: 1. radiation waveguide; 11. output section; 12. polarization separation / forming section; 13. input section; 2. stepped film; 3. left-handed circular polarization feed waveguide; 4. right-handed circular polarization feed waveguide; 5. 90° waveguide bend. DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The present embodiment provides a K-band broadband stepped film waveguide dual circular polarizer, as shown in Figures 1-2 The broadband stepped film waveguide dual circular polarizer is a left-right symmetrical structure, including a left-handed circular polarization feed waveguide, a right-handed circular polarization feed waveguide, two 90° waveguide bends, a radiation waveguide, and a stepped film.

[0032] The left-handed circular polarization feed waveguide and the right-handed circular polarization feed waveguide are rectangular stepped waveguides with the same structure and symmetrical arrangement, and are respectively connected to the radiation waveguide through a 90° waveguide bend, and the cavity part as a whole is in T shape. The rectangular stepped waveguide is an impedance matching waveguide, the size of the input section is the same as that of the standard rectangular waveguide BJ220, the size of the output section is the same as that of the cross section of the 90° waveguide bend, the width, the narrow side and the length of the middle section stepped waveguide are 11.8mm, 5.8mm and 5mm respectively, and the size of the cross section of the 90° waveguide bend is 11.4mm*5.3mm.

[0033] The radiation waveguide in the present embodiment is composed of a square waveguide and a cross waveguide, as shown in Figure 5 (a), and the central axis of the square waveguide coincides with that of the cross waveguide, and the edges of the square waveguide are parallel to the arms of the cross waveguide; Figure 5(b) shows an example of a radiating waveguide consisting of a square waveguide and two cross-shaped waveguides superimposed. In this embodiment, the side length of the square waveguide is 9.2 mm, the arm length of the cross waveguide is 11.4 mm, and the width is 5 mm; the right angles of the inner wall of the radiating waveguide are rounded with a chamfer radius of 1 mm.

[0034] As shown in Figure 4, the radiating waveguide is divided into an input section, a polarization separation / forming section, and an output section connected in sequence, with lengths of 2.3 mm, 16.7 mm, and 7.7 mm, respectively. The input section has a waveguide wall in the middle that divides it into two equal cavities, which are connected to two 90° waveguide bends. The polarization separation / forming section has a stepped diaphragm of uniform thickness, whose height gradually decreases along the direction of electromagnetic wave propagation, merging completely into the output section. The waveguide wall and stepped diaphragm are 0.8 mm thick. From the input section to the output section, the height * length of each segment of the stepped diaphragm are 7.6 mm * 1.3 mm, 4.8 mm * 4.2 mm, 3 mm * 5.4 mm, and 1.6 mm * 5.8 mm, respectively. This invention's radiating waveguide integrates the fundamental mode TE in a square waveguide. 10 Pattern and adjacent higher-order patterns TM 01 and TE 20 By expanding the mode spacing, single-mode transmission of the square waveguide mode can be achieved in a wide bandwidth, thereby eliminating the resonance phenomenon caused by the appearance of higher-order modes in the traditional stepped spacer waveguide dual circular polarizer at high frequencies.

[0035] like Figure 3 As shown, the physical prototype of this embodiment consists of only three parts: a circularly polarized feed waveguide symmetrically cut along its center, two sections (upper and lower) of a 90° waveguide bend, and a radiating waveguide section. To ensure assembly accuracy, locating pins are installed between the three sections. The assembly of the all-metal broadband four-way dual-circularly polarized power divider can be achieved using screws. Clearly, this embodiment has a simple structure and is easy to manufacture and assemble.

[0036] Based on the above embodiments, simulations were performed, and the port reflection performance was as follows: Figure 6 As shown, within a bandwidth of 17-24 GHz, the designed dual circular polarizer exhibits a standing wave ratio (SWR) of less than -20 dB, demonstrating that the broadband stepped diaphragm waveguide dual circular polarizer of this invention can achieve efficient electromagnetic wave transmission.

[0037] Output beam axial ratio performance such as Figure 8 As shown, in the frequency range of 16.5-23.5 GHz, the axial ratio of the circularly polarized beam output by the dual circular polarizer is 0.2 dB, indicating that the broadband stepped diaphragm waveguide dual circular polarizer of the present invention can output high-purity circularly polarized waves.

[0038] Input port isolation performance such as Figure 7As shown, the isolation between the two output ports of the dual circular polarizer is greater than 20 dB in the frequency range of 16.7-24 GHz. In the frequency range of 18.6-23.2 GHz, the isolation between the two output ports of the dual circular polarizer is greater than 30 dB. It is shown that the wideband stepped iris waveguide dual circular polarizer has good port isolation.

[0039] In summary, the wideband stepped iris waveguide dual circular polarizer solves the problem that the working bandwidth of the existing dual circular polarizer cannot cover the entire waveguide working frequency range, and greatly improves the axial ratio, voltage standing wave ratio, port isolation and other performance indicators of the stepped iris waveguide dual circular polarizer.

[0040] Obviously, the above embodiments are only examples for clearly illustrating, but not limit the embodiments. For those skilled in the art, based on the above description, other different forms of changes or variations can also be made. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A broadband stepped-membrane waveguide dual-circular polarizer, characterized by, The broadband stepped film waveguide dual circular polarizer is a left-right symmetrical structure, comprising a left-handed circular polarized feed waveguide, a right-handed circular polarized feed waveguide, two 90-degree waveguide bends, a radiation waveguide and a stepped film; The left-handed circular polarized feed waveguide and the right-handed circular polarized feed waveguide are rectangular stepped waveguides with the same structure and symmetrical arrangement, and are connected to the radiation waveguide through a 90-degree waveguide bend respectively, and the cavity part is in the shape of T as a whole; The radiation waveguide is composed of a square waveguide and at least one cross-shaped waveguide, and the central axes of the square waveguide and the cross-shaped waveguide coincide, two edges of the square waveguide are parallel to one arm of the cross-shaped waveguide, and the other two edges are parallel to the other arm of the cross-shaped waveguide; The radiation waveguide is divided into an input section, a polarization separation / forming section and an output section connected in sequence; the middle part of the input section is provided with a waveguide wall to divide it into left and right two-part cavities, and is in communication with two 90-degree waveguide bends respectively; the polarization separation / forming section is provided with a stepped film with uniform thickness, which gradually decreases in height along the direction of electromagnetic wave propagation, and the left and right two-part cavities are completely fused at the output section.

2. A broadband stepped-membrane waveguide dual-circular polarizer as claimed in claim 1, characterized in that, In the radiation waveguide, the arm length of the cross-shaped waveguide with the longest arm is the same as the length of the wide side of the 90-degree waveguide bend.

3. A broadband stepped-membrane waveguide dual-circular polarizer as claimed in claim 1 or 2, characterized in that, The thickness of the stepped film is greater than 0.2 mm and less than 1 mm.

4. A broadband stepped-membrane waveguide dual-circular polarizer as claimed in claim 3, wherein, The cross section of the radiation waveguide is a symmetrical polygon, and the length of each edge is not less than 1 mm.

5. A broadband stepped-membrane waveguide dual-circular polarizer as claimed in claim 4, wherein, The inner wall of the radiation waveguide is rounded at right angles.

6. A broadband stepped-membrane waveguide dual-circular polarizer as claimed in claim 4, wherein, The broadband stepped film waveguide dual circular polarizer is processed by a numerical control lathe, or is realized by 3D printing and injection molding processing.

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