阅读说明：本技术 一种hmsiw平衡定向耦合器 (HMSIW balance directional coupler ) 是由 孙亮 韩杨昆 朱家明 邢思贝 邓宏伟 于 2019-09-29 设计创作，主要内容包括：本发明公开了一种HMSIW平衡定向耦合器,适用于较高的厘米波和毫米波频段,由两个垂直堆叠的单端定向耦合器组成,在公共地面上刻蚀矩形缝隙并引入人工表面等离激元(SSPP)结构。在差模激励下,矩形缝隙区域被等效为理想电壁(PEC),由于公共金属面近似认为是理想电壁,因此其差模等效电路即对应的单端定向耦合器。然而,在共模激励下时,公共金属面被等效为理想磁壁(PMC)。根据PEC-PMC结构的边界条件,TE<Sub>n0</Sub>模式无法在SIW中传输,此时共模信号在矩形缝隙边缘被反射。通过在矩形缝隙中引入SSPP结构,上/下金属层与公共金属面之间的槽线传输模式被有效抑制,从而进一步提高了平衡定向耦合器的共模抑制能力。另外,本发明具有结构紧凑、设计简单以及高共模抑制等特点。(The invention discloses a HMSIW balanced directional coupler, which is suitable for higher centimeter wave and millimeter wave frequency bands and consists of two single-end directional couplers which are vertically stacked, wherein a rectangular gap is etched on a public ground, and an artificial surface plasmon polariton (SSPP) structure is introduced. Under differential mode excitation, the rectangular slot region is equivalent to an ideal electrical wall (PEC), and since the common metal plane is approximately considered to be an ideal electrical wall, the differential mode equivalent circuit thereof is the corresponding single-ended directional coupler. However, under common mode excitation, the common metal plane is equivalent to an ideal magnetic wall (PMC). TE according to the boundary conditions of the PEC-PMC structure n0 The mode cannot be transmitted in the SIW, when the common mode signal is reflected at the edges of the rectangular slot. By introducing the SSPP structure into the rectangular gap, the slot line transmission mode between the upper/lower metal layers and the common metal surface is effectively inhibited, and the common-mode inhibition capability of the balanced directional coupler is further improved. In addition, the invention has the characteristics of compact structure, simple design, high common mode rejection and the like.)

1. An HMSIW balanced directional coupler, characterized by: comprises an upper dielectric substrate and a lower dielectric substrate; the upper dielectric substrate and the lower dielectric substrate share one metal surface, which is called a common metal surface;

the upper dielectric substrate and the lower dielectric substrate are respectively provided with an HMSIW directional coupler, and the two HMSIW directional couplers are vertically stacked; each HMSIW directional coupler comprises two symmetrical and oppositely arranged HMSIW transmission lines; each HMSIW directional coupler is provided with four balanced ports, and eight balanced ports of the two HMSIW directional couplers form four differential ports; rectangular slits are etched in the common metal face.

2. The HMSIW balanced directional coupler of claim 1, wherein: the four differential ports are respectively a first differential port, a second differential port, a third differential port and a fourth differential port; when a differential mode signal excites the first differential port, the rectangular slot area is equivalent to a PEC surface, the differential signal can be normally transmitted in the HMSIW directional coupler at the moment, the second differential port is a straight-through end, the third differential port is a coupling end, and the fourth differential port is an isolation end; when the common-mode signal excites the first differential port, the rectangular slot area is equivalent to a PMC surface, and at the moment, the common-mode signal is blocked at the edge of the rectangular slot and cannot be normally transmitted.

3. HMSIW balanced directional coupler according to claim 1 or 2, characterized in that: the rectangular gap region is provided with a periodic SSPP structure, and the SSPP structure can enable the frequency corresponding to the slot line transmission mode in the HMSIW balanced directional coupler to be in the cut-off region of the dispersion curve in the SSPP structure, so that the slot line transmission mode can be effectively restrained, and the common mode restraining capability is further improved.

4. The HMSIW balanced directional coupler of claim 3, characterized in that: the bottom of the SSPP structure is connected with the edge of the rectangular gap; by adjusting the height of the SSPP structureh _sThe transmission characteristic of the SSPP structure is changed, and the suppression effect on common-mode signals is further influenced.

5. The HMSIW balanced directional coupler of claim 4, wherein: the SSPP structure that is provided with two symmetries in the rectangle gap region, every SSPP structure all lays along the long limit in rectangle gap, and every SSPP structure all includes that a plurality of all is perpendicular and the even metal strip in interval with the long limit looks in rectangle gap.

6. The HMSIW balanced directional coupler of claim 5, wherein: the size of the rectangular gap is adjusted, and then the suppression effect of the common-mode signal is adjusted.

7. The HMSIW balanced directional coupler of claim 1, wherein: a rectangular upper metal layer is printed at the center of the upper surface of the upper medium substrate; a rectangular lower metal layer is printed at the center of the lower surface of the lower medium substrate; four corner ends of the upper metal layer and the lower metal layer are respectively provided with a feed microstrip line.

8. The HMSIW balanced directional coupler of claim 7, wherein: a coupling window parallel to the long edge is arranged at the symmetrical center of the upper metal layer and the lower metal layer; two through hole belts are symmetrically arranged on two sides of the coupling window, and each through hole belt is formed by linearly arranging a plurality of metal through holes.

9. The HMSIW balanced directional coupler of claim 8, wherein: the length of the rectangular gap is larger than that of the coupling window, two short side edges of the rectangular gap are provided with a through hole ground metal strip located in the rectangular gap, and the through hole ground metal strips correspond to the positions of the corresponding metal through holes.

10. The HMSIW balanced directional coupler of claim 7, wherein: each feed microstrip line comprises a gradual change section and a straight line section; the transition section is connected with the straight line section and the upper metal layer or the lower metal layer.

Technical Field

The invention relates to a coupler, in particular to an HMSIW balanced directional coupler.

Background

In modern wireless communication systems, balancing devices are receiving increasing attention because they can effectively suppress both ambient noise and noise within the system. The balanced directional coupler has the function of distributing the amplitude and phase of the differential signal, and is an indispensable device in communication system equipment. Currently, there are several types of balanced couplers designed by utilizing the branch line and coupling line structure. However, these balanced couplers are difficult to apply to the higher microwave frequency band, mainly to the frequency band below 5GHz, because the stub and the coupled line have large losses (mainly radiation losses) when operating at high frequencies. In addition, these balanced couplers cannot achieve high common mode rejection (noise rejection) over a wide frequency band, and can only achieve common mode rejection of 30dB or more in the vicinity of the differential pass band (several hundred mhz).

The Substrate Integrated Waveguide (SIW) has a structure similar to that of the conventional metal waveguide, and has basically the same propagation characteristics, so that the substrate integrated waveguide has the characteristics of high Q value, strong transmission capability and the like. Meanwhile, the structure of the substrate integrated waveguide is similar to a microstrip structure, and has the characteristics of small volume, light weight, low cost, easiness in processing, high integration level and the like. Therefore, the substrate integrated waveguide has wide application in high-integration microwave systems. Based on the mode distribution characteristics of SIW, half-mode substrate integrated waveguides (HMSIW) have been proposed. The HMSIW can reduce the size by half on the basis of keeping the excellent transmission characteristics of the SIW, and is suitable for the trend of miniaturization of modern wireless communication systems. If the HMSIW transmission line can be applied to the design of the balanced coupler, a balanced coupler suitable for high frequency band and having a compact structure can be designed. However, the transmission characteristics and the structural form of the HMSIW are greatly different from those of the microstrip line and the coupling line, so the existing design method cannot be applied to the HMSIW balanced directional coupler. There is currently no work in designing balanced directional couplers using SIW or HMSIW transmission lines according to the examined literature.

Disclosure of Invention

The present invention provides a HMSIW balanced directional coupler, which is based on a half-mode substrate integrated waveguide (HMSIW) and an artificial surface plasmon polariton (SSPP), has a compact structure, and can be applied to higher centimeter and millimeter wave frequency bands, in order to solve the technical problems of the prior art.

In order to solve the technical problems, the invention adopts the technical scheme that:

an HMSIW balanced directional coupler includes an upper dielectric substrate and a lower dielectric substrate. The upper dielectric substrate and the lower dielectric substrate share one metal surface, which is called a common metal surface.

And one HMSIW directional coupler is arranged on each of the upper dielectric substrate and the lower dielectric substrate, and the two HMSIW directional couplers are vertically stacked. Each HMSIW directional coupler comprises two symmetrical and oppositely arranged HMSIW transmission lines. Each HMSIW directional coupler has four balanced ports, and the eight balanced ports of the two HMSIW directional couplers form four differential ports. Rectangular slits are etched in the common metal face.

The four differential ports are respectively a first differential port, a second differential port, a third differential port and a fourth differential port. When the differential mode signal excites the first differential port, the rectangular slot area is equivalent to a PEC surface, the differential signal can be normally transmitted in the HMSIW directional coupler at the moment, the second differential port is a straight-through end, the third differential port is a coupling end, and the fourth differential port is an isolation end. When the common-mode signal excites the first differential port, the rectangular slot area is equivalent to a PMC surface, and at the moment, the common-mode signal is blocked at the edge of the rectangular slot and cannot be normally transmitted.

The rectangular gap region is provided with a periodic SSPP structure, and the SSPP structure can enable the frequency corresponding to the slot line transmission mode in the HMSIW balanced directional coupler to be in the cut-off region of the dispersion curve in the SSPP structure, so that the slot line transmission mode can be effectively restrained, and the common mode restraining capability is further improved.

The bottom of the SSPP structure is connected to the edges of the rectangular slot. By adjusting the height h of the SSPP structure_sThe transmission characteristic of the SSPP structure is changed, and the suppression effect on common-mode signals is further influenced.

The SSPP structure that is provided with two symmetries in the rectangle gap region, every SSPP structure all lays along the long limit in rectangle gap, and every SSPP structure all includes that a plurality of all is perpendicular and the even metal strip in interval with the long limit looks in rectangle gap.

The size of the rectangular gap is adjusted, and then the suppression effect of the common-mode signal is adjusted.

The center of the upper surface of the upper medium substrate is printed with a rectangular upper metal layer. The center of the lower surface of the lower medium substrate is printed with a rectangular lower metal layer. Four corner ends of the upper metal layer and the lower metal layer are respectively provided with a feed microstrip line.

And a coupling window parallel to the long edge is arranged at the symmetrical center of the upper metal layer and the lower metal layer. Two through hole belts are symmetrically arranged on two sides of the coupling window, and each through hole belt is formed by linearly arranging a plurality of metal through holes.

The length of the rectangular gap is larger than that of the coupling window, two short side edges of the rectangular gap are provided with a through hole ground metal strip located in the rectangular gap, and the through hole ground metal strips correspond to the positions of the corresponding metal through holes.

Each feed microstrip line comprises a transition section and a straight line section. The transition section is connected with the straight line section and the upper metal layer or the lower metal layer.

The invention has the following beneficial effects:

1. the present invention has four pairs of differential ports, respectively a first, second, third and fourth differential port. Under differential mode excitation, if the first differential port is a signal input end, the second differential port is a straight-through end, the third differential port is a coupling end, and the fourth differential port is an isolation end. Due to its symmetrical structure, high speed signals can maintain good integrity when transmitted therein. Under differential mode excitation, the rectangular slot region is equivalent to an ideal electrical wall (PEC), and since the common metal plane is approximately considered to be an ideal electrical wall, the differential mode equivalent circuit thereof is the corresponding single-ended directional coupler. However, under common mode excitation, its middle layer is equivalent to an ideal magnetic wall (PMC). TE according to the boundary conditions of the PEC-PMC structure_n0The mode can not be transmitted in the SIW, and the common-mode signal is totally reflected at the edge of the rectangular gap, so that good common-mode rejection is realized. The use of the HMSIW greatly reduces the size of the coupler relative to conventional SIW balanced directional couplers.

2. The invention can be applied to higher centimeter wave and millimeter wave frequency bands. The invention adopts the SIW transmission line with high quality factor as the main structure, so the invention can be applied to higher frequency band, and the preferred frequency band is 10-40 GHz.

3. The invention can realize-3 dB coupling of differential signals and simultaneously ensure the integrity of the differential signals in the transmission process.

4. The invention can realize good inhibition effect on common mode noise in a wide frequency band (such as 0-60GHz), and reduce the interference of environmental noise, circuit noise and the like on target signals, thereby obviously improving the signal-to-noise ratio in a communication system and improving the communication quality. The common metal plane is equivalent to an ideal magnetic wall (PMC) when under common mode excitation. According to the boundary condition of the PEC-PMC structure, a TEn0 mode cannot be transmitted in the SIW, and at the moment, a common-mode signal is totally reflected at the edge of a rectangular slot, so that good common-mode rejection is realized. In addition, an SSPP structure is loaded on the common metal surface, so that the transmission of a slot line mode is restrained, the common mode rejection is further improved, and a wide frequency band can be realized.

Drawings

Fig. 1 shows a schematic view of a printed circuit board used in the present invention.

Fig. 2 shows a schematic three-dimensional structure of an HMSIW balanced directional coupler according to the present invention.

Fig. 3 shows a top view of a HMSIW balanced directional coupler of the present invention.

Fig. 4(a) shows the signal transmission diagram of the HMSIW balanced directional coupler of the present invention when excited in the differential mode.

Fig. 4(b) shows the signal transmission diagram of the HMSIW balanced directional coupler of the present invention when excited in the common mode.

Fig. 5(a) shows the electric field profile of the two-layer HMSIW transmission line of the present invention under the influence of the slot mode.

Fig. 5(b) shows a transmission coefficient diagram of a two-layer HMSIW transmission line under the influence of a slot mode according to the present invention.

FIG. 6 shows the electric field distribution in the dual-layer HMSIW structure of the present invention when the SPP structural units are loaded.

FIG. 7(a) shows a graph of the differential mode scattering parameter simulation and actual measurement results of the present invention.

Fig. 7(b) shows a graph of the simulation and actual measurement results of the common mode scattering parameters of the present invention.

Fig. 7(c) is a graph showing simulation and measurement results of the phase difference of the through terminal and the coupling terminal under the differential mode excitation according to the present invention.

Among them are:

s1, a medium substrate; s2, an upper metal layer; s3, a lower metal layer;

10. an upper dielectric substrate; 11. a metal layer; 12. a transition section; 13. a straight line segment; 14. a metal via; port1. upper first balanced port; port2. upper second balanced port; port3. upper third balanced port; port4. upper fourth balanced port;

20. a common metal plane; 21. a rectangular slit; 22. a metal strip; 23. a through-hole ground metal strip;

30. a lower dielectric substrate; port 1'. lower first balanced port; port 2'. lower second balanced port; port 3'. lower third balanced port; port 4'. the fourth balanced port.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific preferred embodiments.