A broadband orthogonal mode coupler based on gap waveguide

Abstract

The present invention relates to a broadband orthogonal mode coupler based on a gap waveguide, and belongs to the field of microwave device technology. The present invention solves the problem that traditional orthogonal mode couplers are often difficult to process in scenarios with higher frequency bands. It comprises an upper metal plate, a lower metal plate and pins, and both the upper metal plate and the lower metal plate have pins. There is a gap between the corresponding pins on the upper metal plate and the pins on the lower metal plate, and there are a horizontal polarization power divider, a vertical polarization mode transition structure, and a double-ridge orthogonal junction arranged in sequence between the upper metal plate and the lower metal plate. Since the double-ridge orthogonal junction of the present invention adopts an oblique input method, the designed ridge structure can have a larger width, and still has a processable size for the higher frequency segment. On the basis of adopting the gap waveguide, the processing difficulty of the structure is further reduced, and the lateral size of the entire orthogonal mode coupler is also reduced.

Description

Technical Field

[0001] The invention relates to a broadband orthogonal mode coupler, belonging to the technical field of microwave devices. Background Art

[0002] Passive millimeter-wave imaging technology is a method of imaging that uses the temperature difference between the brightness of the imaging target and the background as imaging information. It has the advantages of high concealment and all-weather performance. Currently, polarization imaging technology, as a supplement to passive millimeter-wave imaging technology, has significantly improved the imaging quality and target information acquisition performance. However, the feed antennas of traditional passive millimeter-wave imaging systems, including cone horn antennas or dielectric rod antennas, can only generate electromagnetic waves in a single polarization mode and cannot meet the requirements of dual-polarization passive millimeter-wave imaging systems. There are currently two main ways to implement feed antennas with dual-polarization performance: one is to design an antenna with dual-polarization performance, usually using an array synthesis method, which has a more complex structure and is difficult to design the antenna feeding network; the other is to achieve dual-polarization performance in the antenna feeding stage. The main method currently used is to use an orthogonal mode coupler to achieve the synthesis of two mutually orthogonal linear polarization modes.

[0003] Orthogonal-mode couplers, also known as polarization duplexers or orthogonal-mode converters, are used to separate or synthesize orthogonal modes within the same frequency band and are one way a feed can achieve dual-polarization performance. Orthogonal-mode couplers, which input mutually orthogonal modes through two input channels and output them through a common output port, are currently widely used in communications, aerospace, remote sensing imaging, and other fields. Orthogonal-mode couplers primarily utilize waveguides. Due to the relatively high frequency bands used in passive millimeter-wave imaging, the corresponding orthogonal-mode couplers are physically small and difficult to manufacture.

[0004] Therefore, there is an urgent need to propose a broadband orthogonal mode coupler based on gap waveguide to solve the above technical problems. Summary of the Invention

[0005] The present invention addresses the difficulty in fabricating traditional orthogonal-mode couplers for use in higher-frequency bands. It provides a broadband orthogonal-mode coupler based on gap waveguides. A brief overview of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important aspects of the present invention, nor is it intended to limit the scope of the present invention.

[0006] The technical solution of the present invention:

[0007] A broadband orthogonal mode coupler based on a gap waveguide includes an upper metal plate, a lower metal plate and pins. Both the upper metal plate and the lower metal plate have pins. There is a gap between the corresponding pins on the upper metal plate and the pins on the lower metal plate. A horizontal polarization power divider, a vertical polarization mode transition structure and a double-ridge orthogonal junction are sequentially arranged between the upper metal plate and the lower metal plate.

[0008] Preferably, one end of the upper metal plate and the lower metal plate both have a horizontally polarized feeding channel, the two horizontally polarized feeding channels are correspondingly arranged to form a horizontally polarized power splitter, the middle part of the horizontally polarized power splitter has a T-shaped channel, the vertical slot of the T-shaped channel is connected to the horizontally polarized feeding port, and the two ends of the transverse slot of the T-shaped channel are connected to the horizontally polarized power splitter port.

[0009] Preferably, the connection portion between the vertical groove and the transverse groove of the T-shaped channel has a step matching structure.

[0010] Preferably: the other end of the upper metal plate and the lower metal plate both have a Y-shaped groove, the two Y-shaped grooves are correspondingly arranged to form a double-ridged orthogonal junction, the vertical groove of the double-ridged orthogonal junction is a common port, the oblique groove of the double-ridged orthogonal junction is a horizontally polarized feeding port, and the horizontally polarized power splitter port of the horizontally polarized power splitter is connected to the horizontally polarized feeding port of the double-ridged orthogonal junction.

[0011] Preferably: one end of the Y-shaped vertical groove is connected to two symmetrically arranged oblique grooves, the connection part of the Y-shaped vertical groove and the oblique groove has a stepped double-ridge structure, and the stepped double-ridge structures correspondingly arranged on the upper metal plate and the lower metal plate form a double-ridge matching structure.

[0012] Preferably, a vertical polarization feeding port is provided in the middle of the upper metal plate, and a stepped matching structure is provided on the middle of the lower metal plate. The corresponding vertical polarization feeding port and stepped matching structure form a vertical polarization mode transition structure.

[0013] Preferably, there is a gap between the vertical polarization feeding port and the stepped double-ridge structure on the upper metal plate, and there is a gap between the stepped matching structure and the stepped double-ridge structure on the lower metal plate, and the two corresponding gaps form a vertical polarization feeding channel.

[0014] Preferably, the upper metal plate and the lower metal plate both have straight slots in the middle, and the corresponding straight slots form two connecting slots. The horizontal polarization power splitter port of the horizontal polarization power splitter is connected to the horizontal polarization feed port of the double-ridged orthogonal junction through the connecting slot, and a vertical polarization mode transition structure is provided between the two connecting slots.

[0015] The present invention has the following beneficial effects:

[0016] The present invention adopts a double-layer processing structure, which is easy to process and has the advantages of large bandwidth, good port isolation, large mechanical strength, etc. Since the gap waveguide is adopted to realize waveguide port feeding, no additional conversion structure is required, and the feeding method is relatively simple.

[0017] The upper metal plate and the lower metal plate of the present invention each have a layer of pins of the same height, and there is an air gap between the two layers of pins to form an electromagnetic bandgap structure. The higher frequency segment has the advantages of easier processing and more compact structure.

[0018] Since the double-ridge orthogonal junction of the present invention adopts an oblique input method, the designed ridge structure can have a larger width and still have a processable size for the higher frequency segment. On the basis of adopting the gap waveguide, the processing difficulty of the structure is further reduced, and the lateral size of the entire orthogonal mode coupler is also reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a main view of a broadband orthogonal mode coupler based on a gap waveguide;

[0020] Figure 2 yes Figure 1 Middle AA section view;

[0021] Figure 3 This is an exploded view of a broadband orthogonal mode coupler based on a gap waveguide;

[0022] Figure 4 It is a structural diagram of the upper metal plate;

[0023] Figure 5 It is a structural diagram of the lower metal plate;

[0024] Figure 6 It is a stereogram of a broadband orthogonal mode coupler based on a gap waveguide;

[0025] Figure 7 It is a structural diagram of a horizontally polarized power divider;

[0026] Figure 8 It is a structural diagram of a double-ridge orthogonal junction;

[0027] Figure 9 Schematic diagram of the structure of the vertical polarization mode transition structure;

[0028] Figure 10 is the S parameter of the horizontally polarized power divider;

[0029] Figure 11 These are the S parameters of a broadband orthogonal mode coupler based on gap waveguide.

[0030] In the figure: 1-upper metal plate, 2-lower metal plate, 3-pin, 4-horizontally polarized power divider, 5-double-ridged orthogonal junction, 6-vertical polarization mode transition structure, 11-vertical polarization feed port, 21-stepped matching structure, 122-stepped double-ridge structure, 123-stepped matching structure, 124-horizontally polarized feed channel, 125-connecting slot, 126-Y-shaped slot, 127-vertically polarized feed channel, 128-three-level double-ridged matching structure. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0032] Specific implementation method 1: Combination Figure 1-11 This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide, comprising an upper metal plate 1, a lower metal plate 2 and a pin 3. The upper metal plate 1 is arranged parallel to the lower metal plate 2 and can be fixed by bolts. The upper metal plate 1 and the lower metal plate 2 both have pins 3. An air gap is provided between the corresponding pins 3 on the upper metal plate 1 and the pins 3 on the lower metal plate 2. A horizontal polarization power divider 4, a vertical polarization mode transition structure 6, and a double-ridge orthogonal junction 5 are sequentially provided between the upper metal plate 1 and the lower metal plate 2. The present invention adopts a double-layer processing method. The structure is convenient for processing. At the same time, the non-contact electromagnetic bandgap transmission line structure of the gap waveguide is utilized. Periodically arranged pins are introduced into the parallel plate waveguide to form an equivalent PMC (Perfect Magnetic Conductor) surface to guide the directional propagation of electromagnetic waves. The slot gap waveguide and the ridge gap waveguide are all-metal structures with the advantages of large bandwidth, good port isolation, and large mechanical strength. Due to the use of the gap waveguide, waveguide port feeding can be realized by designing the feeding port without the need for an additional conversion structure, and the feeding method is relatively simple.

[0033] Specific implementation method 2: Combination Figure 1-11 This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. The upper metal plate 1 and the lower metal plate 2 each have a horizontally polarized feeding channel 124 at one end. The two horizontally polarized feeding channels 124 are correspondingly arranged to form a horizontally polarized power splitter 4. The middle part of the horizontally polarized power splitter 4 has a T-shaped channel. The vertical slot of the T-shaped channel is connected to the horizontally polarized feeding port, and the two ends of the transverse slot of the T-shaped channel are connected to the horizontally polarized power splitter port.

[0034] Specific implementation method three: Combination Figure 1-11This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. One end of the vertical slot of the T-shaped channel is connected to the middle of the transverse slot. The connection between the vertical slot and the transverse slot of the T-shaped channel has a step matching structure 123. A three-stage double-ridge matching structure 128 is provided on the transverse slot of the T-shaped channel at a position corresponding to the step matching structure. The horizontal polarization power splitter is based on a half-height slot gap waveguide, that is, a gap waveguide designed with a half-height pin structure. It is a three-port network and uses two sections of slot gap waveguides of different widths as the step matching structure 123. The step matching structure 123 and the three-stage double-ridge matching structure achieve good matching. The upper metal plate 1 and the lower metal plate 2 of the half-height pin slot gap waveguide each have a layer of pins of the same height. There is an air gap between the two layers of pins, forming an electromagnetic bandgap structure. It has similar electromagnetic characteristics to the traditional pin-type slot gap waveguide, but has the advantages of easier processing and more compact structure in the higher frequency range. The performance of the gap waveguide is similar to that of the metal waveguide. During the design process, the designed horizontal polarization power divider can be analyzed using the analysis method of the traditional metal waveguide. Therefore, the designed horizontal polarization power divider has the advantages of large bandwidth, high feeding efficiency, compact structure and low processing difficulty. At the same time, since the input port has the same size as the standard waveguide, the waveguide can be used to directly feed the horizontal polarization mode electromagnetic wave. The stepped slot gap waveguide structure and the three-level double-ridge matching structure can achieve equal energy distribution and good matching of the input and output ports.

[0035] Specific implementation method four: Combination Figure 1-11 This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. The other ends of the upper metal plate 1 and the lower metal plate 2 each have a Y-shaped slot 126. The two Y-shaped slots 126 are correspondingly arranged to form a channel of the double-ridged orthogonal junction 5. The vertical slot of the double-ridged orthogonal junction 5 channel is a common port, and the oblique slot of the double-ridged orthogonal junction 5 channel is a horizontally polarized feeding port. The horizontally polarized power splitter port of the horizontally polarized power splitter 4 is connected to the horizontally polarized feeding port of the double-ridged orthogonal junction 5.

[0036] Specific implementation method five: Combination Figure 1-8This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. One end of the vertical slot of the Y-shaped slot 126 is connected to two symmetrically arranged oblique slots. The connection portion of the vertical slot of the Y-shaped slot 126 and the oblique slot has a stepped double-ridge structure. The cross-section of the vertical slot of the Y-shaped slot 126 is larger than the cross-section of the oblique slot. The stepped double-ridge structures 122 correspondingly arranged on the upper metal plate 1 and the lower metal plate 2 form a double-ridge matching structure. The double-ridge orthogonal junction 5 is realized based on a half-height slot gap waveguide. The horizontal polarization input channel (oblique slot) adopts an oblique 45° input. At the same time, a double-ridge matching structure is adopted to improve its electrical performance. The designed double-ridge matching structure includes a first-level trapezoidal ridge and three-level rectangular ridges of different sizes, which can simultaneously achieve matching performance for vertical polarization and horizontal polarization feeding ports. The adjustment of the double-ridge matching structure is achieved by adopting the oblique input method, so that the designed double-ridge matching structure can have a larger width and still have a processable size for the higher frequency segment. On the basis of adopting the gap waveguide, the processing difficulty of the structure is further reduced, and the lateral size of the entire orthogonal mode coupler is also reduced; a narrower feeding channel (Y-slot) is used to feed the two polarization modes. Due to the large size difference, the structure is guaranteed to have good isolation for the two polarization modes, which solves the problem of difficult processing caused by the use of a more sophisticated structure in the conventional design of orthogonal mode couplers to achieve good matching and isolation. The gap waveguide layered processing and the oblique input to increase the structure size make the proposed orthogonal mode coupler suitable for high-frequency processing design.

[0037] Specific implementation method six: combination Figure 1-11 This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. The upper metal plate 1 has a vertical polarization feeding port 11 in the middle, and the lower metal plate 2 has a stepped matching structure 21 in the middle. The corresponding vertical polarization feeding port 11 and the stepped matching structure 21 form a vertical polarization mode transition structure 6.

[0038] Specific implementation method seven: combination Figure 1-11 This embodiment describes a broadband orthogonal mode coupler based on a gap waveguide. A gap is provided between the vertical polarization feeding port 11 and the stepped double-ridge structure on the upper metal plate 1 , and a gap is provided between the stepped matching structure 21 and the stepped double-ridge structure on the lower metal plate 2 . The two corresponding gaps form a vertical polarization feeding channel 127 .

[0039] Specific implementation method eight: combination Figure 1-11The present embodiment is described. In the present embodiment, a broadband orthogonal mode coupler based on a gap waveguide is provided. A straight slot is provided in the middle of the upper metal plate 1 and the lower metal plate 2. The corresponding straight slots form two parallel connecting slots 125. The horizontal polarization power splitter port of the horizontal polarization power splitter 4 is connected to the horizontal polarization feeding port of the double-ridged orthogonal junction 5 through the connecting slot 125. A vertical polarization mode transition structure 6 is provided between the two connecting slots 125. The vertical polarization feeding port 11 and the vertical polarization feeding channel 127 are vertically arranged. The vertical polarization feeding port can realize high-efficiency feeding, and is suitable for a 90° turn transition structure of the vertical polarization mode. A stepped matching structure 21 is adopted to realize low-loss conversion of the feeding direction from vertical to horizontal. At the same time, the feeding port has the same size as the standard waveguide port, and direct feeding of the waveguide port can be realized, and the feeding method is relatively simple.

[0040] The present invention forms a broadband orthogonal mode coupler based on a gap waveguide by using a horizontally polarized power divider based on a half-height gap waveguide and a double-ridge orthogonal junction. By adopting a half-height slot gap waveguide and an orthogonal junction horizontal polarization channel oblique input mode, the overall structure is simplified, and the performance of a wide bandwidth and high port isolation is achieved in a relatively simple structure. At the same time, the present invention has the practical application advantages of high overall mechanical strength of the structure and low processing difficulty. The problems of the current dual-polarization feed source having a single design mode, a narrow working bandwidth, and a high processing difficulty can be solved. The present invention can well meet the feed source requirements of a passive millimeter wave imaging system using dual linear polarization and can be applied to the system.

[0041] The present invention is a W-band slot-gap waveguide broadband orthogonal mode coupler. The present invention includes a horizontal polarization power splitter and a double-ridge orthogonal junction. The present invention can be made of copper metal. The S parameters of the horizontal polarization power splitter based on the slot-gap waveguide are as follows: Figure 10 As shown, the horizontally polarized feed port is the input port of the horizontally polarized mode, i.e., port 1, and the two horizontally polarized power splitter ports are the output ports, i.e., port 2 and port 3. The designed example can achieve broadband performance in the W band; Figure 11 The figure shows the S parameters of the designed orthogonal mode coupler, where S HH is the reflection coefficient of the horizontal polarization input port, S VV is the reflection coefficient of the vertically polarized input port, S VH To improve the isolation between the two polarization modes, the designed orthogonal mode coupler can cover the bandwidth of the W band as a whole, with a relative bandwidth of up to 30%. At the same time, the isolation of the two polarization input channels is greater than 70dB, achieving broadband and high isolation working performance with a relatively simple structure.

[0042] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutations and combinations. Therefore, the present invention will no longer describe the technical solutions after permutations and combinations one by one, but it should be understood that the technical solutions after permutations and combinations have been disclosed by the present invention.

[0043] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A broadband orthogonal mode coupler based on a gap waveguide, characterized in that: The invention comprises an upper metal plate (1), a lower metal plate (2) and a pin (3), wherein the upper metal plate (1) and the lower metal plate (2) both have the pin (3), a gap is provided between the corresponding pin (3) on the upper metal plate (1) and the pin (3) on the lower metal plate (2), and a horizontal polarization power divider (4), a vertical polarization mode transition structure (6), and a double-ridge orthogonal junction (5) are provided in sequence between the upper metal plate (1) and the lower metal plate (2); One end of each of the upper metal plate (1) and the lower metal plate (2) is provided with a horizontal polarization feeding channel (124), and the two horizontal polarization feeding channels (124) are correspondingly arranged to form a horizontal polarization power splitter (4). The middle portion of the horizontal polarization power splitter (4) is provided with a T-shaped channel, the vertical slot of the T-shaped channel is connected to the horizontal polarization feeding port, and both ends of the transverse slot of the T-shaped channel are connected to the horizontal polarization power splitter port. The other ends of the upper metal plate (1) and the lower metal plate (2) are both provided with a Y-shaped slot (126), and the two Y-shaped slots (126) are correspondingly arranged to form a double-ridge orthogonal junction (5), the vertical slot of the double-ridge orthogonal junction (5) is a common port, the oblique slot of the double-ridge orthogonal junction (5) is a horizontal polarization feeding port, and the horizontal polarization power splitter port of the horizontal polarization power splitter (4) is connected to the horizontal polarization feeding port of the double-ridge orthogonal junction (5); One end of the vertical groove of the Y-shaped groove (126) is connected to two symmetrically arranged oblique grooves, and the connection portion of the vertical groove of the Y-shaped groove (126) and the oblique groove has a stepped double-ridge structure, and the stepped double-ridge structures (122) correspondingly arranged on the upper metal plate (1) and the lower metal plate (2) form a double-ridge matching structure; The upper metal plate (1) has a vertical polarization feeding port (11) in the middle, and the lower metal plate (2) has a stepped matching structure (21) in the middle. The correspondingly arranged vertical polarization feeding port (11) and stepped matching structure (21) form a vertical polarization mode transition structure (6).

2. The broadband orthogonal mode coupler based on gap waveguide according to claim 1, characterized in that: The connection portion between the vertical groove and the transverse groove of the T-shaped channel has a step matching structure (123).

3. The broadband orthogonal mode coupler based on gap waveguide according to claim 1, characterized in that: There is a gap between the vertical polarization feeding port (11) and the stepped double-ridge structure on the upper metal plate (1), and there is a gap between the stepped matching structure (21) and the stepped double-ridge structure on the lower metal plate (2), and the two corresponding gaps form a vertical polarization feeding channel (127).

4. The broadband orthogonal mode coupler based on gap waveguide according to claim 3, characterized in that: The upper metal plate (1) and the lower metal plate (2) both have straight slots in the middle, and the corresponding straight slots form two connecting slots (125). The horizontal polarization power splitter port of the horizontal polarization power splitter (4) and the horizontal polarization feed port of the double-ridge orthogonal junction (5) are connected through the connecting slot (125), and a vertical polarization mode transition structure (6) is provided between the two connecting slots (125).

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