A fourth-order butler matrix feeding network based on air waveguide

Abstract

A fourth-order butler matrix feeding network based on air waveguide consists of four 3db couplers, two 0db cross junctions, two ‑45° phase shifters and two 0° phase shifters. There is a partition of specific size on both sides of the 3db coupler, and the same output amplitude of the two ports is achieved by short-wall slit coupling; the 0db cross junction is formed by cascading two 3db couplers; the 0° phase shifter and the ‑45° phase shifter achieve phase change by changing the waveguide width. Compared with the traditional microstrip form, the air waveguide has the advantages of low insertion loss and high power. The butler matrix feeding network composed of the above structure not only has equal output amplitudes of the four ports and can maintain a phase difference of ±10° in the 27‑31GHz frequency band, but also has the advantages of compact structure, high port isolation, high power and low loss.

Description

Technical Field

[0001] The invention relates to the field of communication technology, and in particular to a fourth-order butler matrix feeding network based on air waveguide. Background Art

[0002] With the rapid development of mobile communication technology and the sharp increase in mobile communication business volume, we are facing problems such as strong signal interference between communication cells, insufficient spectrum capacity and narrow signal coverage. Multi-beam antennas can generate directional pattern characteristics of multiple beams at the same time, which can increase network capacity; in addition, multi-beam antennas can easily achieve narrow beams and high gain, which can reduce signal interference and increase coverage distance. Therefore, multi-beam antennas have broad application prospects and value. Among them, the Butler matrix is ​​an important component of the multi-beam antenna and a key component for generating multi-beam characteristics. However, the Butler matrix in the prior art has a complex structure and high loss, which needs to be further improved.

[0003] Most of the existing butler matrix feeding networks are based on microstrip lines or substrate integrated waveguides. However, microstrip lines have large losses in high frequency bands, small power capacity and low quality factor. For these reasons, the butler matrix based on microstrip lines is not suitable for working in the millimeter wave band. The substrate integrated waveguide uses a metal wire array to realize the waveguide wall. There are certain gaps, which easily cause energy leakage, resulting in poor out-of-band suppression performance of the filter, which is more serious in broadband conditions. In addition, the substrate integrated waveguide is essentially a dielectric-filled waveguide, and the dielectric has certain losses, which are more obvious in the KA band. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the present invention proposes a fourth-order butler matrix feeding network based on air waveguide. The loss of the butler matrix formed by the air waveguide is very small even in the KA band.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A fourth-order butler matrix feeding network based on air waveguide is composed of a rectangular air waveguide, one side of which has four input ports, the four input ports correspond to the input ports of two 3db couplers respectively, the two 3db couplers are coupled through a 0db cross junction, two -45° phase shifters are added on both sides of the first 0db cross junction respectively, two 0° phase shifters are added on both sides of the second 0db cross junction respectively, the two 0db cross junctions are connected through two 3db couplers, the output port of the second 0db cross junction and the output ports of the two 0° phase shifters are the four output ports of the entire matrix, forming the entire fourth-order butler matrix feeding network; wherein:

[0007] The two partitions and the short wall slits on the upper and lower sides of the 3db directional coupler are located at the center of the entire 3db coupler;

[0008] The 0db crossover junction is formed by cascading two 3db couplers;

[0009] The 0° phase shifter is a convex portion in the straight waveguide, and the convex portions are symmetrical about the center of the entire 0° phase shifter;

[0010] The -45° phase shifter is a concave portion in a straight waveguide, and the concave portions are symmetrical about the center of the entire -45° phase shifter.

[0011] Furthermore, in the fourth-order butler matrix feeding network, in the structure except the phase shifter, all waveguides have a width of 7.2 mm and a height of 3.5 mm, and are designed according to the required operating frequency band.

[0012] Furthermore, the thickness of the upper and lower baffles of the 3db coupler is 0.8mm, the length of the baffle is 6mm, the length of the short wall slit is 9.5mm, and it is designed based on the optimal transmission coefficient and isolation of the coupler.

[0013] Furthermore, the height of the raised portion of the 0° phase shifter is 1.8 mm, the length of the raised portion is 36 mm, the angle of the raised position and the X-axis is 45°, and the design is based on the optimal phase change amplitude of the 0° phase shifter.

[0014] Furthermore, the height of the recessed portion of the -45° phase shifter is 1.2 mm, the length of the recessed portion is 30 mm, the angle of the recessed position to the X-axis is 30°, and the design is based on the optimal phase change amplitude of the -45° phase shifter.

[0015] Furthermore, no other medium is provided in the entire butler matrix, which is composed entirely of air cavity waveguides.

[0016] The beneficial effects of the present invention are:

[0017] (1) Using the phase change caused by the 3db coupler and two phase shifters, the phase difference between the four output ports is maintained at 45°;

[0018] (2) Use 3db coupler and 0db cross junction to achieve equal amplitude output of four output ports;

[0019] (3) The phase shifter in this network is realized by changing the waveguide width. Compared with the traditional phase shifter that increases the length of the transmission line, this method avoids the extension and bending of the transmission line and has a relatively small volume.

[0020] (4) This network is based on air waveguides and does not use any lossy media, which can achieve theoretically lossless transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a top view of a 3db coupler in an embodiment of the present invention.

[0022] Figure 2 It is a top view of a cross-junction of 0db in an embodiment of the present invention.

[0023] Figure 3 It is a top view of a cross-sectional view of a -45° phase shifter in an embodiment of the present invention.

[0024] Figure 4 is a top view of a 0° phase shifter in an embodiment of the present invention.

[0025] Figure 5 is a top view of the butler matrix in an embodiment of the present invention.

[0026] Figure 6 1 is a top view of a butler matrix in an embodiment of the present invention.

[0027] Figure 7 1 is a side view of an input port of a butler matrix in an embodiment of the present invention.

[0028] Figure 8 4 is a side view of an output port of a butler matrix in an embodiment of the present invention.

[0029] Fig. 9 It is a 3D diagram of the Butler matrix in an embodiment of the present invention.

[0030] Fig.10 It is a simulation result diagram of input port return loss and isolation in an embodiment of the present invention.

[0031] Fig.11 4 is a diagram showing the simulation results of the output amplitude of the output port in an embodiment of the present invention.

[0032] Fig.12 3 is a diagram showing the simulation results of the output phase difference of the output port in an embodiment of the present invention.

[0033] Description of the drawings: 1- 3db coupler, 2- 0db cross junction, 3- -45° phase shifter, 4- 0° phase shifter. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0035] The present invention provides a fourth-order butler matrix feeding network based on air waveguide, the overall top view and cross-sectional view are as follows: Figure 5-8 As shown, the left side is the input port and the right side is the output port. The overall 3D diagram is as follows Fig. 9 As shown. The entire butler matrix consists of four major parts: 3db coupler, 0db cross junction, -45° phase shifter and 0° phase shifter. Figure 1 This is a cross-sectional view of a 3db coupler, with a short wall gap opened between two waveguide transmission lines, and a layer of partitions attached to the upper and lower sides of the two waveguide transmission lines; Figure 2 This is a cross-sectional view of a 0db crossover junction, which is formed by cascading two 3db couplers; Figure 3 This is a cross-sectional view of a 0° phase shifter. Because the phase shifter is a phase change relative to a 0db cross junction, the lower half of the phase shifter is a 0db cross junction, and the upper half is a straight waveguide transmission line. The middle of this waveguide transmission line is recessed, and the phase propagation coefficient of the waveguide is changed in this way to achieve the effect of phase shift. Figure 4 It is a cross-sectional view of a -45° phase shifter. Its design concept is basically the same as that of a 0° phase shifter. The only difference is that increasing the width of the waveguide can more easily achieve a -45° phase difference, rather than reducing the width of the waveguide.

[0036] Combination Figure 5A fourth-order butler matrix feeding network based on air waveguide is composed of a rectangular air waveguide, one side of which has four input ports, the four input ports correspond to the input ports of two 3db couplers respectively, the two 3db couplers are coupled through a 0db cross junction, two -45° phase shifters are added on both sides of the first 0db cross junction respectively, two 0° phase shifters are added on both sides of the second 0db cross junction respectively, the two 0db cross junctions are connected through two 3db couplers, the output port of the second 0db cross junction and the two The output ports of the 0° phase shifters are the four output ports of the entire matrix, forming the entire fourth-order butler matrix feeding network; among them: the two partitions on the upper and lower sides of the 3db directional coupler and the short wall slits are located at the center of the entire 3db coupler; the 0db cross junction is formed by cascading two 3db couplers; the 0° phase shifter is a convex part in the straight waveguide, and the convex parts are symmetrical about the center of the entire 0° phase shifter; the -45° phase shifter is a concave part in the straight waveguide, and the concave parts are symmetrical about the center of the entire -45° phase shifter.

[0037] The fourth-order butler matrix feeding network based on air waveguide, in the structure except the phase shifter, all the waveguides are 7.2mm wide and 3.5mm high.

[0038] In the 3db coupler 1, the thickness of the upper and lower partitions is 0.8 mm, the length of the partition is 6 mm, and the length of the short wall slit is 9.5 mm.

[0039] The 0db crossover junction 2 is formed by cascading two 3db couplers.

[0040] The height of the recessed portion in the -45° phase shifter 3 is 1.2 mm, the length of the recessed portion is 30 mm, and the angle of the recessed position to the X-axis is 30°.

[0041] The height of the raised portion in the 0° phase shifter 4 is 1.8 mm, the length of the raised portion is 36 mm, and the angle of the raised position is 45° with the X-axis.

[0042] The simulation results of Example 1 when the port is fed are as follows Figure 10 to Figure 12 As shown, Fig.10 The isolation and return loss of the input port shown are both lower than -15db in the 27-31GHz band, and even lower than -20db in the 27.5-31GHz band; Fig.12 The phase differences of the output ports shown are all within the range of -45°±10° in the 27-31 GHz frequency band, indicating that the return loss, isolation and phase characteristics of the Butler matrix of the present invention are all very good. Fig.11Shown are the output amplitudes of the four output ports. Within 27-31 GHz, the transmission coefficients fluctuate within the range of -6±0.6 db, and the loss is very small.

[0043] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A fourth-order butler matrix feeding network based on air waveguide, characterized in that: The fourth-order butler matrix feeding network is composed of a rectangular air waveguide, one side of which has four input ports, the four input ports correspond to the input ports of two 3db couplers respectively, the two 3db couplers are coupled through a 0db cross junction, two -45° phase shifters are added on both sides of the first 0db cross junction respectively, two 0° phase shifters are added on both sides of the second 0db cross junction respectively, the two 0db cross junctions are connected through two 3db couplers, the output port of the second 0db cross junction and the output ports of the two 0° phase shifters are the four output ports of the entire matrix, forming the entire fourth-order butler matrix feeding network; wherein: The two partitions and the short wall slits on the upper and lower sides of the 3db coupler are located at the center of the entire 3db coupler; The 0db crossover junction is formed by cascading two 3db couplers; The 0° phase shifter is a convex portion in the straight waveguide, and the convex portions are symmetrical about the center of the entire 0° phase shifter; The -45° phase shifter is a concave portion in a straight waveguide, and the concave portions are symmetrical about the center of the entire -45° phase shifter.

2. The fourth-order butler matrix feeding network based on air waveguide according to claim 1, characterized in that: The fourth-order butler matrix feeding network, in the structure except the phase shifter, has all waveguides with a width of 7.2 mm and a height of 3.5 mm, and is designed according to the required operating frequency band.

3. The fourth-order butler matrix feeding network based on air waveguide according to claim 1, characterized in that: The thickness of the upper and lower baffles of the 3db coupler is 0.8mm, the length of the baffle is 6mm, and the length of the short wall slit is 9.5mm. It is designed based on the optimal transmission coefficient and isolation of the coupler.

4. The fourth-order butler matrix feeding network based on air waveguide according to claim 1, characterized in that: The height of the raised portion of the 0° phase shifter is 1.8 mm, the length of the raised portion is 36 mm, the angle of the raised position is 45° with the X-axis, and the design is based on the optimal phase change amplitude of the 0° phase shifter.

5. The fourth-order butler matrix feeding network based on air waveguide according to claim 1, characterized in that: The height of the recessed portion of the -45° phase shifter is 1.2 mm, the length of the recessed portion is 30 mm, and the angle of the recessed position to the X-axis is 30°. The design is based on the optimal phase change amplitude of the -45° phase shifter.

6. The fourth-order butler matrix feeding network based on air waveguide according to claim 1, characterized in that: There is no other medium in the entire butler matrix, which is composed of air cavity waveguides.

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