Butler matrix feed network with slow wave structure

Abstract

The invention belongs to the field of wireless communication, and particularly relates to a Butler matrix feed network with a slow wave structure, which comprises 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-degree slow wave loading phase shifter, a second 45-degree slow wave loading phase shifter, a first 0-degree slow wave loading phase shifter and a second 0-degree slow wave loading phase shifter. According to the Butler matrix feed network, a row of non-radiation transverse slots are introduced into each phase shifter to serve as phase delay lines, so that the structure size of the Butler matrix feed network is reduced, and the dispersion is reduced.

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] As a passive beamforming feeding network, the Butler Matrix (BM) can be applied to passive phased array feeding. It is equipped with 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, the traditional Butler Matrix usually uses equal-length and unequal-width phase shifters or equal-width and unequal-length phase shifters when shifting the phase. 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, resulting in poor phase consistency of the Butler Matrix feeding network 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, 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, 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 object of the present invention is to provide a Butler matrix feeding network with a slow-wave structure, combining rectangular non-radiative transverse slots with equal-length and unequal-width phase shifters to reduce the structural size of the Butler matrix feeding 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 solution:

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

[0008] 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;

[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, and the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; 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 have the same structure, all 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, all consisting of a first metal layer, a dielectric layer, a second metal layer, and a third substrate integrated waveguide metal via. The four slow-wave loaded phase shifters also have the same structure, all 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 the second metal layer and penetrating 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 in sequence 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-radiative transverse grooves are arranged at equal intervals.

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

[0021] In the SIW-based phase shifter design of the present invention, the combination of equal length and unequal width phase shifters and etching a row of rectangular non-radiative transverse grooves is to achieve phase consistency, reduce dispersion and achieve miniaturization. The following is an inferential description to explain this principle:

[0022] Regarding equal-length and unequal-width phase shifters: According to transmission line theory, when the width of a transmission line changes, its characteristic impedance will also change. When the length is equal, the parts with different widths will cause the electromagnetic waves to propagate at different speeds, thereby causing phase changes. However, this structure will show certain dispersion characteristics at different frequencies, that is, the change of phase with frequency is not linear, which will affect the consistency of the phase.

[0023] Therefore, a row of rectangular non-radiative transverse grooves running through the second metal layer is etched in the phase shifter to change the electromagnetic field distribution inside the SIW. This change will cause the phase of the electromagnetic wave to change when passing through the structure. The key is that the dispersion characteristics generated by etching a row of rectangular non-radiative transverse grooves and the dispersion characteristics of equal-length and unequal-width phase shifters are different at different frequencies. After introducing a row of rectangular non-radiative transverse grooves in the phase shifter, the difference in the dispersion characteristics of the two can be used to compensate each other. At lower frequencies, equal-length and unequal-width phase shifters may produce large phase deviations, while the dispersion characteristics of etched rectangular non-radiative transverse grooves can offset this deviation to a certain extent, making the overall phase change closer to linear, thereby improving phase consistency. Similarly, at higher frequencies, the interaction between the two can also play a similar compensation effect and reduce the impact of dispersion.

[0024] In addition, by adjusting the parameters of the phase shifter and the etched rectangular non-radiative transverse grooves, such as the phase shifter width and the size of the groove, the best match at different frequencies can be achieved. This method can not only improve the consistency of the phase and reduce the dispersion, but also optimize the entire structure to a certain extent and achieve miniaturization. By utilizing the characteristics of these two structures, there is no need to add a large number of additional components or structures to achieve performance improvement, which helps 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 phase delay lines 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 feeding network structure matching degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a waveguide Butler matrix system integrated on a 60-GHz substrate with 0° phase shifter, cross coupler, and 45° phase shifter, as well as simulated field distribution diagrams for excitation of 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 is a schematic diagram of a substrate integrated waveguide coupler structure having fixed phase shifters of different widths;

[0031] Figure 4is a network block diagram of a Butler matrix with 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 with a slow-wave structure;

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

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

[0036] Fig. 9 is a comparison diagram of the phase delay line sizes of the Butler matrix with slow-wave structure and with and without rectangular slow-wave structure in the embodiment;

[0037] Fig.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] Fig.11 is the magnitude of the S-parameter of the Butler matrix simulation of the embodiment with the slow-wave structure;

[0039] Fig.12 The embodiment is a Butler matrix with a slow-wave structure emulating the phase difference of the output port when each input port is excited. DETAILED DESCRIPTION

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

[0041] like Figure 4-Figure 5 As shown, the present embodiment provides a Butler matrix feeding network with a slow-wave structure, comprising a first metal layer, a dielectric substrate, a second metal layer, and a Butler matrix feeding network stacked in sequence 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 in the figure correspond to the first to fourth input ports of this embodiment, and ports 5 to 8 correspond to the first to fourth output ports in the embodiment.

[0042] Two rows of metallized through holes are arranged 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, and the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; 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, and are all composed 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, and are all composed 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, and are all composed of a first metal layer, a dielectric layer, a second metal layer, a second substrate integrated waveguide metal via, and a groove arranged on the second metal layer and penetrating the second metal layer.

[0051] When the first input port is excited, the phase difference of the fifth to eighth output ports is -45°; when the second input port is excited, the phase difference of the fifth to eighth output ports is 135°; when the third input port is excited, the phase difference of the fifth to eighth output ports is -135°; when the fourth input port is excited, the phase difference of the output ports is 45°. In this embodiment, the phase is shifted by adjusting the width of each group of non-radiative transverse grooves and substrate integrated waveguides.

[0052] In implementation, in order to improve the matching degree of the Butler matrix feeding network structure. In this embodiment, each non-radiative transverse slot in the phase shifter is composed of a plurality of rectangular slots, such as Figure 6 As shown, a 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. In each group of non-radial 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. The plurality of rectangular grooves in each group of non-radial transverse grooves are arranged at equal intervals. Figure 7 4 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 feeding 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] Fig. 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 shifters in the Butler matrix feed network of this embodiment are shown. Fig. 9As shown, this embodiment is compared based on a 45° phase delay. The left side is a phase shifter based on a combination of a rectangular non-radiative transverse slot and an equal-length unequal-width phase shifter in this embodiment, and the length of the phase shifter is Lr1; the right side is a traditional equal-length unequal-width phase shifter, and the length of the phase shifter is Lr2. Among them, Lr1 is 3.08mm, Lr2 is 5.28mm, and the phase shifter in this embodiment is reduced by 41.7% in size compared to the traditional phase shifter, and has the characteristics of miniaturization.

[0055] Fig.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 and the traditional equal-length unequal-width phase shifters in the Butler matrix feed network of this embodiment are shown, as shown in FIG. Fig.10 As shown, Fig.10 The left side is 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, which can be obtained within 1° within 135GHz to 145GHz; the right side is the phase difference of the traditional equal-length unequal-width phase shifter, which can be obtained within 15.5° within 135GHz to 145GHz. The 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 has the characteristics of low dispersion and good phase consistency compared with the traditional equal-length unequal-width phase shifters.

[0056] Fig.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] Fig.12 It is the phase difference of the output port when each input port of the Butler matrix simulation with a slow-wave structure in the embodiment is excited. In the Butler matrix feeding network with a slow-wave structure in this embodiment, within 135GHz to 145GHz, when the first input port is excited, the phase difference value of the fifth to eighth output ports fluctuates around -45°; when the second input port is excited, the phase difference value of the fifth to eighth output ports fluctuates around 135°; when the third input port is excited, the phase difference value of the fifth to eighth output ports fluctuates around -135°; 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 a row of non-radiative transverse slots is introduced into each phase shifter of the Butler matrix feeding network as a phase delay line, thereby achieving a reduction in the structural size and dispersion of the Butler matrix feeding network.

[0059] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined 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; two rows of metalized 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; 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, and the through end is connected to the input end of the first 0° slow-wave loaded phase shifter; 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, and are all composed of a first metal layer, a dielectric layer, a second metal layer, a second substrate integrated waveguide metal via, and a groove arranged on the second metal layer and penetrating 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 is composed 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-radiative 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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