A Butler matrix feeding network with slow-wave structure

Abstract

The present invention belongs to the field of wireless communications and specifically relates to a Butler matrix feed network with a slow-wave structure, comprising a substrate integrated waveguide and a Butler matrix feed network formed on the substrate integrated waveguide; the Butler matrix feed network comprises a first 3dB coupler, a second 3dB coupler, a third 3dB coupler, a fourth 3dB coupler, a first cross coupler, a second cross coupler, a first 45° slow-wave loaded phase shifter, a second 45° slow-wave loaded phase shifter, a first 0° slow-wave loaded phase shifter, and a second 0° slow-wave loaded phase shifter. The present invention reduces the size of the Butler matrix feed network structure and reduces dispersion by introducing a row of non-radiative transverse slots as a phase delay line in each phase shifter.

Description

Technical Field

[0001] The invention belongs to the field of wireless communications, and in particular relates to a Butler matrix feeding network with a slow-wave structure. Background Art

[0002] The Butler Matrix (BM) is a passive beamforming feeding network that can be used for passive phased array feeding. It has N input ports and N output ports, and the input and output ports are isolated from each other. The Butler Matrix is ​​mainly composed of four parts: a 3dB coupler, a cross coupler, a 45° phase shifter, and a 0° phase shifter. It has the characteristics of multi-beam forming, simple structure, and high isolation. However, when shifting the phase, the traditional Butler Matrix usually uses equal-length and unequal-width phase shifters or equal-width and unequal-length phase shifters. Among them, equal-length and unequal-width phase shifters will increase the width, and equal-width and unequal-length phase shifters will increase the length, and both structures have serious dispersion problems, which makes the Butler Matrix feeding network have poor phase consistency within the working frequency band.

[0003] For example, the document "IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES" proposes a waveguide Butler matrix system integrated on a 60-GHz substrate, such as Figure 1 As shown in FIG, a curved substrate integrated waveguide (SIW) is used to achieve phase delay, which will increase the size in the width direction. Figure 2 As shown in the figure, the dispersion phenomenon is serious and the phase consistency is poor within the working frequency band.

[0004] For example, the document "2007 IEEE / MTT-S International Microwave Symposium" discloses a substrate integrated waveguide coupler with fixed phase shifters of different widths. Figure 3 As shown in the figure, the metal through-hole structure of SIW is very suitable for achieving a fixed phase difference by using different SIW widths. Therefore, the article realizes an equal-length SIW fixed phase shifter for the first time, but the size of the phase shifter increases in the width direction. Summary of the Invention

[0005] The purpose of the present invention is to provide a Butler matrix feed network with a slow-wave structure, which combines rectangular non-radiative transverse slots with equal-length and unequal-width phase shifters to reduce the structural size of the Butler matrix feed network, reduce dispersion, and improve phase consistency within the operating frequency band.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A Butler matrix feed network with a slow-wave structure comprises a first metal layer, a dielectric substrate, a second metal layer, and a Butler matrix feed network stacked in sequence from bottom to top;

[0008] Two rows of metallized through holes are provided in the dielectric substrate, and the first metal layer and the second metal layer are connected by metal vias to form a substrate integrated waveguide;

[0009] The Butler matrix feeding network is formed on a substrate integrated waveguide, and includes a first 3dB coupler, a second 3dB coupler, a third 3dB coupler, a fourth 3dB coupler, a first cross coupler, a second cross coupler, a first 45° slow-wave loaded phase shifter, a second 45° slow-wave loaded phase shifter, a first 0° slow-wave loaded phase shifter, and a second 0° slow-wave loaded phase shifter, wherein:

[0010] The input end and the isolation end of the first 3dB coupler constitute the first input end and the second input end of the entire structure respectively. The through end of the first 3dB coupler is connected to the input end of the first 45° slow-wave loaded phase shifter, and the coupling end is connected to the input end of the first cross coupler.

[0011] The output end of the first 45° slow-wave loaded phase shifter is connected to the input end of the second 3dB coupler;

[0012] The isolation end of the second 3dB coupler is connected to the through end of the first cross coupler, the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; and the coupling end is connected to the input end of the second cross coupler;

[0013] The output end of the first 0° slow-wave loaded phase shifter constitutes the first output end of the entire structure;

[0014] The input end and the isolation end of the third 3dB coupler constitute the third input end and the fourth input end of the Butler matrix feeding network respectively; the through end of the third 3dB coupler is connected to the isolation end of the first cross coupler, and the coupling end is connected to the input end of the second 45° slow-wave loaded phase shifter;

[0015] The output end of the second 45° slow-wave loaded phase shifter is connected to the isolation end of the fourth 3dB coupler; the input end of the fourth 3dB coupler is connected to the coupling end of the first cross-coupler, the through end is connected to the isolation end of the second cross-coupler, and the coupling end is connected to the input end of the second 0° slow-wave loaded phase shifter; the through end of the second cross-coupler constitutes the second output end of the entire structure, and the coupling end constitutes the third output end of the entire structure; the output end of the second 0° slow-wave loaded phase shifter constitutes the fourth output end of the entire structure;

[0016] The four 3dB couplers share the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, and metal vias in the first substrate-integrated waveguide. The two cross-couplers share the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, and metal vias in the third substrate-integrated waveguide. The four slow-wave loaded phase shifters also share the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, metal vias in the second substrate-integrated waveguide, and a groove located on and extending through the second metal layer.

[0017] Furthermore, each group of non-radiating transverse grooves is composed of a plurality of rectangular grooves, and the plurality of rectangular grooves are arranged in a row along a straight line, and the length Wr of the rectangular grooves decreases gradually from the center to both ends.

[0018] Furthermore, in each group of non-radiating transverse grooves, the rectangular groove located in the middle is used as the symmetry axis, and the number of rectangular grooves on both sides is equal, so that the overall distribution is symmetrical.

[0019] Furthermore, the plurality of rectangular grooves in each group of non-radiating transverse grooves are arranged at equal intervals.

[0020] Furthermore, the dielectric substrate is a quartz substrate.

[0021] In the SIW-based phase shifter design, the present invention combines equal-length, unequal-width phase shifters with a row of etched rectangular, non-radiative transverse slots to achieve phase consistency, reduce dispersion, and achieve miniaturization. The following is a deductive explanation of this principle:

[0022] Regarding equal-length, unequal-width phase shifters: According to transmission line theory, varying the width of a transmission line will also alter its characteristic impedance. While the length is equal, varying widths will cause electromagnetic waves to propagate at different speeds, leading to phase shifts. However, this structure exhibits certain dispersion characteristics at different frequencies, meaning that the phase variation with frequency is not linear, which can affect phase consistency.

[0023] Therefore, a row of rectangular non-radiative transverse slots is etched through the second metal layer in the phase shifter to alter the electromagnetic field distribution within the SIW. This change causes the phase of the electromagnetic wave to shift as it passes through the structure. Crucially, the dispersion characteristics produced by etching a row of rectangular non-radiative transverse slots differ from those of a phase shifter with equal length and unequal width at different frequencies. By introducing a row of rectangular non-radiative transverse slots into the phase shifter, the difference in their dispersion characteristics can be exploited to compensate for each other. At lower frequencies, a phase shifter with equal length and unequal width may produce significant phase deviation, but the dispersion characteristics of the etched rectangular non-radiative transverse slots can offset this deviation to a certain extent, making the overall phase change more linear and thus improving phase consistency. Similarly, at higher frequencies, the interaction between the two can also achieve a similar compensatory effect, reducing the impact of dispersion.

[0024] Furthermore, by adjusting the parameters of the phase shifter and the etched rectangular non-radiative transverse slots, such as the phase shifter width and slot size, optimal coordination can be achieved at different frequencies. This approach not only improves phase consistency and reduces dispersion, but also optimizes the overall structure to a certain extent, achieving miniaturization. By leveraging the characteristics of these two structures, performance improvements can be achieved without the need for a large number of additional components or structures, thereby helping to reduce the size of the entire phase shifter.

[0025] After adopting the above technology, the present invention has the following advantages:

[0026] 1. The present invention reduces the size of the Butler matrix feed network structure and reduces dispersion by introducing a row of non-radiative transverse slots as a phase delay line in each phase shifter.

[0027] 2. The present invention uses the rectangular slot located in the middle of each group of non-radiating transverse slots as the symmetry axis, and the number of rectangular slots on both sides is equal, so that the overall distribution is symmetrical, thereby obtaining a better Butler matrix feed network structure matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure shows the simulated field distribution of the waveguide Butler matrix system with 0° phase shifter, cross coupler, and 45° phase shifter integrated on a 60-GHz substrate, as well as the excitations at ports 1, 5, and 7.

[0029] Figure 2 is the relative phase diagram of the 4*4 substrate integrated waveguide Butler matrix excited by the second input terminal;

[0030] Figure 3 1. is a schematic diagram of the structure of a substrate integrated waveguide coupler with fixed phase shifters of different widths;

[0031] Figure 4is a network block diagram of a Butler matrix having a slow-wave structure according to an embodiment;

[0032] Figure 5 is a schematic diagram of a Butler matrix structure with a slow-wave structure according to an embodiment;

[0033] Figure 6 The embodiment is a phase delay line structure of a rectangular transverse groove slow-wave structure in a Butler matrix having a slow-wave structure;

[0034] Figure 7 2 is a simulation result of a Butler matrix 45° phase delay line with a slow-wave structure according to an embodiment;

[0035] Figure 8 is a simulation result of a Butler matrix 0° phase delay line with a slow-wave structure according to an embodiment;

[0036] Figure 9 3. This is a comparison diagram of the phase delay line sizes of the Butler matrix with a slow-wave structure and with and without a rectangular slow-wave structure according to an embodiment;

[0037] Figure 10 is the phase difference of the phase delay line with and without the rectangular slow-wave structure of the Butler matrix of the embodiment;

[0038] Figure 11 is the magnitude of the S-parameter of the Butler matrix simulation of the embodiment having the slow-wave structure;

[0039] Figure 12 It is the phase difference of the output port when each input port is stimulated by the Butler matrix with a slow-wave structure in the embodiment. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0041] like Figure 4-Figure 5 As shown, the present embodiment provides a Butler matrix feed network with a slow-wave structure, comprising a first metal layer, a dielectric substrate, a second metal layer, and a Butler matrix feed network stacked sequentially from bottom to top. Figure 4 Port1-Port4 in the figure correspond to the first to fourth input ports of this embodiment, and Port5-Port8 correspond to the first to fourth output ports of this embodiment. Figure 5 Ports 1 to 4 correspond to the first to fourth input ports of this embodiment, and ports 5 to 8 correspond to the first to fourth output ports of the embodiment.

[0042] Two rows of metallized through holes are provided in the dielectric substrate, and the first metal layer and the second metal layer are connected by metal vias to form a substrate integrated waveguide; during implementation, the metal through holes of the substrate integrated waveguide are realized by TGV stamping and metal sputtering processes.

[0043] like Figure 4 As shown, the Butler matrix feeding network is formed on a substrate integrated waveguide, including a first 3dB coupler, a second 3dB coupler, a third 3dB coupler, a fourth 3dB coupler, a first cross coupler, a second cross coupler, a first 45° slow-wave loaded phase shifter, a second 45° slow-wave loaded phase shifter, a first 0° slow-wave loaded phase shifter, and a second 0° slow-wave loaded phase shifter, wherein:

[0044] The input end and the isolation end of the first 3dB coupler constitute the first input end and the second input end of the entire structure respectively. The through end of the first 3dB coupler is connected to the input end of the first 45° slow-wave loaded phase shifter, and the coupling end is connected to the input end of the first cross coupler.

[0045] The output end of the first 45° slow-wave loaded phase shifter is connected to the input end of the second 3dB coupler;

[0046] The isolation end of the second 3dB coupler is connected to the through end of the first cross coupler, the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; and the coupling end is connected to the input end of the second cross coupler.

[0047] The output end of the first 0° slow-wave loaded phase shifter constitutes the first output end of the entire structure;

[0048] The input end and the isolation end of the third 3dB coupler constitute the third input end and the fourth input end of the Butler matrix feeding network respectively; the through end of the third 3dB coupler is connected to the isolation end of the first cross coupler, and the coupling end is connected to the input end of the second 45° slow-wave loaded phase shifter;

[0049] The output end of the second 45° slow-wave loaded phase shifter is connected to the isolation end of the fourth 3dB coupler; the input end of the fourth 3dB coupler is connected to the coupling end of the first cross-coupler, the through end is connected to the isolation end of the second cross-coupler, and the coupling end is connected to the input end of the second 0° slow-wave loaded phase shifter; the through end of the second cross-coupler constitutes the second output end of the entire structure, and the coupling end constitutes the third output end of the entire structure; the output end of the second 0° slow-wave loaded phase shifter constitutes the fourth output end of the entire structure;

[0050] In this embodiment, the four 3dB couplers have the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, and a first substrate integrated waveguide metal via. The two cross couplers have the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, and a third substrate integrated waveguide metal via. Figure 6As shown, the four slow-wave loaded phase shifters also have the same structure, which is composed of a first metal layer, a dielectric layer, a second metal layer, a second substrate integrated waveguide metal via, and a groove provided on and passing through the second metal layer.

[0051] When the first input port is excited, the phase difference between the fifth through eighth output ports is -45°; when the second input port is excited, the phase difference between the fifth through eighth output ports is 135°; when the third input port is excited, the phase difference between the fifth through eighth output ports is -135°; and when the fourth input port is excited, the phase difference between the output ports is 45°. This embodiment achieves phase shifting by adjusting the width of each group of non-radiative transverse slots and substrate-integrated waveguide.

[0052] In order to improve the matching degree of the Butler matrix feeding network structure, the non-radiative transverse slots in each phase shifter of this embodiment are composed of multiple rectangular slots, such as Figure 6 As shown, multiple rectangular grooves are arranged in a row along a straight line, and the lengths Wr of the rectangular grooves decrease gradually from the center to the ends. In each group of non-radial transverse grooves, the central rectangular groove serves as the axis of symmetry, with an equal number of rectangular grooves on either side, resulting in a symmetrical distribution. The multiple rectangular grooves in each group of non-radial transverse grooves are evenly spaced. Figure 7 This is the simulation result of the Butler matrix 45° phase delay line with slow wave structure in the embodiment. Figure 7 It can be seen that the return loss of the 45° phase delay line in the Butler matrix feed network of the slow-wave structure of this embodiment is better than 23.72 dB in the range of 135 GHz to 145 GHz, the insertion loss is better than 0.18 dB, and the phase error of the 45° phase delay line is within 1°.

[0053] Figure 8 is the simulation result of the Butler matrix 0° phase delay line with a slow-wave structure in the embodiment; Figure 8 It can be seen that the return loss of the 0° phase delay line in the Butler matrix feeding network of the slow-wave structure of this embodiment is better than 19.8dB in the range of 135GHz to 145GHz, the insertion loss is better than 0.13dB, and the phase error of the 0° phase delay line is within 3°.

[0054] Figure 9 The comparison results of the phase delay line size of the phase shifter based on the combination of rectangular non-radiative transverse slots and equal-length unequal-width phase shifters and the traditional equal-length unequal-width phase shifter in the Butler matrix feed network of this embodiment are shown. Figure 9As shown in the figure, this embodiment is compared based on a 45° phase retardation. The left side shows the phase shifter of this embodiment, which combines rectangular non-radiating transverse slots with equal-length, unequal-width phase shifters. The length of this phase shifter is Lr1. The right side shows a traditional equal-length, unequal-width phase shifter. The length of this phase shifter is Lr2. Lr1 is 3.08mm, and Lr2 is 5.28mm. Compared to traditional phase shifters, the phase shifter of this embodiment is 41.7% smaller, demonstrating its miniaturization.

[0055] Figure 10 The phase difference comparison results of the phase shifter based on the combination of rectangular non-radiative transverse slots and equal-length unequal-width phase shifters in the Butler matrix feed network of this embodiment and the traditional equal-length unequal-width phase shifter are shown. Figure 10 As shown, Figure 10 The left side shows the phase difference of the phase shifter based on the combination of rectangular non-radiative transverse slots and equal-length, unequal-width phase shifters in this embodiment, achieving a phase error within 1° from 135 GHz to 145 GHz. The right side shows the phase difference of a traditional equal-length, unequal-width phase shifter, achieving a phase error within 15.5° from 135 GHz to 145 GHz. Simulation results show that the phase shifter based on the combination of rectangular non-radiative transverse slots and equal-length, unequal-width phase shifters proposed in this embodiment exhibits lower dispersion and better phase consistency than traditional equal-length, unequal-width phase shifters.

[0056] Figure 11 It is the amplitude of the S parameter of the Butler matrix simulation with a slow-wave structure in the embodiment; the simulation results of the Butler matrix feeding network of the slow-wave structure of this embodiment, taking the excitation first port as an example, show that the return loss of the Butler matrix is ​​better than 13.74dB and the insertion loss is 6dB±1.5dB.

[0057] Figure 12 This embodiment simulates the phase difference of the output ports when each input port is excited in a Butler matrix simulation with a slow-wave structure. In the Butler matrix feed network of this embodiment with a slow-wave structure, within the 135 GHz to 145 GHz range, when the first input port is excited, the phase difference values ​​of the fifth to eighth output ports fluctuate around -45°; when the second input port is excited, the phase difference values ​​of the fifth to eighth output ports fluctuate around 135°; when the third input port is excited, the phase difference values ​​of the fifth to eighth output ports fluctuate around -135°; and when the fourth input port is excited, the values ​​of the fifth to eighth output ports fluctuate around 45°.

[0058] The Butler matrix feeding network of this embodiment is implemented based on substrate integrated waveguide, and by introducing a row of non-radiative transverse slots as phase delay lines in each phase shifter of the Butler matrix feeding network, the structural size of the Butler matrix feeding network is reduced and the dispersion is reduced.

[0059] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A Butler matrix feed network with a slow-wave structure, comprising a first metal layer, a dielectric substrate, a second metal layer, and a Butler matrix feed network stacked in sequence from bottom to top; the dielectric substrate is provided with two rows of metalized through holes, and the first metal layer and the second metal layer are connected by metal vias to form a substrate-integrated waveguide; characterized in that: The Butler matrix feeding network is formed on a substrate integrated waveguide, and includes a first 3dB coupler, a second 3dB coupler, a third 3dB coupler, a fourth 3dB coupler, a first cross coupler, a second cross coupler, a first 45° slow-wave loaded phase shifter, a second 45° slow-wave loaded phase shifter, a first 0° slow-wave loaded phase shifter, and a second 0° slow-wave loaded phase shifter, wherein: The input end and the isolation end of the first 3dB coupler constitute the first input end and the second input end of the entire structure respectively. The through end of the first 3dB coupler is connected to the input end of the first 45° slow-wave loaded phase shifter, and the coupling end is connected to the input end of the first cross coupler. The output end of the first 45° slow-wave loaded phase shifter is connected to the input end of the second 3dB coupler; The isolation end of the second 3dB coupler is connected to the through end of the first cross coupler, the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; and the coupling end is connected to the input end of the second cross coupler. The output end of the first 0° slow-wave loaded phase shifter constitutes the first output end of the entire structure; The input end and the isolation end of the third 3dB coupler constitute the third input end and the fourth input end of the Butler matrix feeding network respectively; the through end of the third 3dB coupler is connected to the isolation end of the first cross coupler, and the coupling end is connected to the input end of the second 45° slow-wave loaded phase shifter; The output end of the second 45° slow-wave loaded phase shifter is connected to the isolation end of the fourth 3dB coupler; the input end of the fourth 3dB coupler is connected to the coupling end of the first cross-coupler, the through end is connected to the isolation end of the second cross-coupler, and the coupling end is connected to the input end of the second 0° slow-wave loaded phase shifter; the through end of the second cross-coupler constitutes the second output end of the entire structure, and the coupling end constitutes the third output end of the entire structure; the output end of the second 0° slow-wave loaded phase shifter constitutes the fourth output end of the entire structure; The four slow-wave loaded phase shifters also have the same structure, consisting of a first metal layer, a dielectric layer, a second metal layer, a second substrate integrated waveguide metal via, and a groove provided on and passing through the second metal layer.

2. The Butler matrix feed network with a slow-wave structure according to claim 1, characterized in that: Each group of non-radiating transverse grooves consists of a plurality of rectangular grooves, which are arranged in a row along a straight line, and the length Wr of the rectangular grooves decreases gradually from the center to both ends.

3. The Butler matrix feed network with a slow-wave structure according to claim 2, characterized in that: In each group of non-radiating transverse grooves, the rectangular groove located in the middle is used as the symmetry axis, and the number of rectangular grooves on both sides is equal, so that the overall distribution is symmetrical.

4. The Butler matrix feed network with a slow-wave structure according to claim 3, characterized in that: The plurality of rectangular grooves in each group of non-radiating transverse grooves are arranged at equal intervals.

5. A Butler matrix feed network with a slow-wave structure according to any one of claims 1 to 4, characterized in that: The dielectric substrate is a quartz substrate.

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