CN110611144B

CN110611144B - Miniaturized broadband forward wave directional coupler unit circuit

Info

Publication number: CN110611144B
Application number: CN201910902077.0A
Authority: CN
Inventors: 于正永; 易鑫; 施永荣; 钱建波; 王志勃; 乔琪; 丁胜高; 张悦
Original assignee: Jiangsu Vocational College of Electronics and Information
Current assignee: Jiangsu Vocational College of Electronics and Information
Priority date: 2019-09-17
Filing date: 2019-09-17
Publication date: 2021-09-03
Anticipated expiration: 2039-09-17
Also published as: CN110611144A

Abstract

The invention discloses a miniaturized broadband forward wave directional coupler unit circuit. The forward wave directional coupler unit circuit has a five-layer circuit structure. The slotted coupling microstrip line is positioned on the first layer of the whole circuit, the interdigital metal parallel plates are positioned on the second layer and the third layer of the whole circuit, and the slotted coupling microstrip line and the interdigital metal parallel plates are connected through a metal through hole; the vertical folding metal wire is folded and bent to the middle position of the fourth layer from the middle position of the second layer, and the layers are connected through metal through holes; the fifth layer is the reference ground of the whole circuit. And a substrate medium is arranged between each metal layer of the five-layer circuit structure. The cascade connection of 5 unit circuits increases the accumulated phase difference of odd-even mode, realizes 0.5dB energy coupling degree in the frequency band of 5.5-9GHz, and the relative coupling bandwidth reaches 48.27%. The forward wave directional coupler unit circuit greatly reduces the size of the whole circuit, and has a simpler structure and stronger practicability.

Description

Miniaturized broadband forward wave directional coupler unit circuit

Technical Field

The invention belongs to the field of passive microwave devices, and particularly relates to a miniaturized broadband forward wave directional coupler unit circuit.

Background

The directional coupler is a passive microwave device capable of distributing energy according to a certain proportion, and is often integrated in various microwave and millimeter wave circuits.

There are two coupling mechanisms of the directional coupler: backward coupling and forward coupling. The coupling strength of backward coupling is determined by the characteristic impedance difference of odd-even mode, and the coupling strength of forward coupling is determined by the phase difference of odd-even mode; compared with backward coupling, the coupler based on the forward coupling mechanism (forward wave directional coupler) can achieve higher coupling strength and can reach 0dB under ideal conditions. In practical design, the techniques adopted by the directional coupler are mainly divided into three types: (1) the coupling is realized by utilizing a branch section structure or a waveguide, and the defects of narrow bandwidth, low coupling degree and large size are overcome, so that the requirement of integration of a modern miniaturized circuit system cannot be met; (2) introducing a Defected Ground Structure (DGS) into a reference Ground plane of the coupling microstrip line, and increasing the phase difference between odd and even modes, thereby reducing the circuit size and realizing energy coupling, but the coupling bandwidth of the DGS Structure is narrow and an additional impedance matching Structure is needed; (3) the multilayer circuit technology relates to the main technology of multilayer PCB technology and Low Temperature Co-Fired Ceramic (LTCC) technology. The present invention employs a third technique.

Disclosure of Invention

The invention aims to provide a miniaturized broadband forward wave directional coupler unit circuit, which realizes high coupling degree of broadband and reduces the circuit size. Through the cascade connection of 5 units, the invention achieves 0.5dB coupling strength in a frequency band of 5.5-9GHz, meanwhile, the straight-through, isolation and standing wave are all below-10 dB, the coupling relative bandwidth reaches 48.27%, the structure is simple, and the practicability is strong.

The technical scheme adopted by the invention is as follows:

the forward wave directional coupler unit circuit has a five-layer circuit structure, and comprises a pair of coupling microstrip lines 1 with grooves in the middle of the top layer, two groups of interdigital metal parallel plates 2, four metal through holes 3, second to fourth layers of metal wirings 4, four metal through holes 5 connected with the second to fourth layers of metal wirings 4, a reference ground plane 6 and a dielectric substrate 7; the slotted coupling microstrip line 1 is positioned on the first layer of the whole circuit; the interdigital metal parallel plates 2 are respectively positioned on the second layer and the third layer of the whole circuit, and the upper metal plate and the lower metal plate of the interdigital metal parallel plates are connected with the slotted coupling microstrip line 1 on the first layer through metal via holes 3; the second to fourth layers of metal wiring lines 4 and four metal via holes 5 connecting the second to fourth layers of metal wiring lines 4 form a vertical folding metal wire; the reference ground plane 6 is the fifth layer of the overall circuit.

The miniaturized broadband forward wave directional coupler unit circuit provided by the invention utilizes the advantages of a multilayer circuit, realizes series interdigital capacitors by adopting an interdigital metal parallel plate structure, folds metal interconnection lines in the vertical direction, reasonably utilizes the circuit area and realizes parallel folding inductors. For the excitation of the even mode, the slotted coupling microstrip line and the interdigital metal parallel plate form a series interdigital capacitor, because a symmetrical plane can be equivalent to an ideal magnetic wall, a plurality of layers of vertical folding metal wires can be equivalent to an open circuit, a series resonance point is introduced into the whole circuit, and the even mode can be transmitted at a proper frequency point; for odd-mode excitation, as a symmetrical plane can be equivalent to an ideal electric wall, the midpoint of an interconnection line between interdigital metal parallel plates can be equivalent to a virtual ground, an inductor connected to the ground in parallel is introduced, and the whole circuit forms a composite right/left hand (CRLH) transmission line and has a series resonance point and a parallel resonance point; the phase starting points of the odd-even modes can be separated by reasonably adjusting the parallel resonance points, the phase difference between the odd-even modes is increased (each unit circuit provides 36-degree phase difference), and the circuit size is reduced. Through the cascade connection of 5 unit circuits, the forward wave directional coupler realizes the energy coupling of 0.5dB in the frequency range of 5.5-9GHz, and simultaneously can keep good impedance matching and realize the miniaturization of the circuit.

Drawings

Fig. 1 is a schematic diagram of a three-dimensional structure of a miniaturized broadband forward wave directional coupler unit circuit provided by the present invention.

Fig. 2 is a top view of a miniaturized broadband forward wave directional coupler unit circuit provided by the present invention.

Fig. 3 is a schematic circuit subdivision diagram of the miniaturized broadband forward wave directional coupler unit provided by the invention.

FIG. 4 is a diagram of the cell provided by the present inventionMM for modeling wideband forward wave directional coupler unit circuit₁A cross-sectional view.

FIG. 5 shows a LL of a miniaturized wideband forward wave directional coupler unit circuit according to the present invention₁A cross-sectional view.

Fig. 6 is a diagram showing a simulation result of scattering parameters (S parameters) after 5 unit circuits of the present invention are cascaded.

Wherein the reference numerals are as follows: MM (Measure and Regulation)₁The coupling microstrip line is a symmetrical plane of the slotted coupling microstrip line in the direction vertical to the x axis; LL (LL)₁Is a cross section of the parallel metal plates in the direction perpendicular to the x-axis.

Detailed Description

The following describes a specific embodiment of a miniaturized wideband forward wave directional coupler unit circuit provided by the present invention with reference to the accompanying drawings:

with reference to fig. 1 and fig. 2, the miniaturized broadband forward wave directional coupler unit circuit provided by the present invention has a five-layer circuit structure, which includes a pair of coupling microstrip lines 1 slotted in the middle of the top layer, two sets of interdigital metal parallel plates 2, four metal via holes 3, second to fourth layers of metal wirings 4, four metal via holes 5 connected to the second to fourth layers of metal wirings 4, a reference ground plane 6 and a dielectric substrate 7; the slotted coupling microstrip line 1 is positioned on the first layer of the whole circuit; the interdigital metal parallel plates 2 are respectively positioned on the second layer and the third layer of the whole circuit, and the upper metal plate and the lower metal plate of the interdigital metal parallel plates are connected with the slotted coupling microstrip line 1 on the first layer through metal via holes 3; the second to fourth layers of metal wiring lines 4 and four metal via holes 5 connecting the second to fourth layers of metal wiring lines 4 form a vertical folding metal wire; the reference ground plane 6 is the fifth layer of the overall circuit. The invention adopts LTCC process, the dielectric material is FerrooA 6M, and the relative dielectric constant epsilon_rWhen the loss tangent tan δ is 5.9, the loss tangent tan δ is 0.002, and the dielectric constant is large, which is advantageous for miniaturization of circuit size. The line width w of the slotted coupling microstrip line is 1.8mm, the coupling spacing s is 1.2mm, the unit period d is 6mm, the width m of the folding metal line is 0.15mm, and the distance w between the folding metal line and the slotted coupling microstrip line is₁The length L of one side of the folded metal wire is 1.2mm, which is 0.3 mm.

FIG. 3 is a schematic circuit diagram of a miniaturized broadband forward wave directional coupler unit, MM, according to the present invention₁The coupling microstrip line is a symmetrical plane of the slotted coupling microstrip line in the direction vertical to the x axis; LL (LL)₁Is a cross section of the parallel metal plates in the direction perpendicular to the x-axis.

FIG. 4 shows an MM of the miniaturized broadband forward wave directional coupler unit circuit provided by the present invention₁The metal wire is vertically folded from the middle position of a second layer of the whole circuit to the middle position of a fourth layer, the layers are connected through metal through holes, the radius r of each through hole is 0.075mm, and the thicknesses of 3 layers of media between the first layer and the fourth layer are all h₁0.098mm, and 1.176mm of overall circuit medium thickness h.

FIG. 5 shows a LL of a miniaturized wideband forward wave directional coupler unit circuit according to the present invention₁And the section reflects the vertical distribution of the interdigital metal parallel plate and the slotted coupling microstrip line. L of coupling microstrip line at the central line of unit circuit₁A groove is formed at the position of 2, the groove width g is 0.15mm, the groove is connected with the interdigital metal parallel plates of the second layer and the third layer through a metal through hole, and the length L of the overlapping region of the parallel plates is₁＝0.4mm。

FIG. 6 shows the simulation results of scattering parameters (S parameters) after 5 units are cascaded according to the present invention, wherein S is₁₁Represents standing wave, S₂₁Is the output of the through terminal, S₃₁For coupling the port outputs, S₄₁To isolate the port output. For odd-even mode excitation, the forward wave directional coupler unit circuit realizes 180 DEG accumulated phase difference in the frequency range of 5.5-9GHz and has the highest coupling strength S₃₁Up to 0.5dB, a coupling bandwidth up to 48.27%, and standing wave S in a frequency range of 5.8-9GHz₁₁A straight-through end S₂₁And isolating port S₄₁All are below-10 dB, the structure is simple, and the practicability is strong.

Claims

1. A miniaturized broadband forward wave directional coupler unit circuit, characterized in that: the miniaturized broadband forward wave directional coupler unit circuit has a five-layer circuit structure, and comprises two coupling microstrip lines (1) with grooves in the middle, two sets of interdigital metal parallel plates (2), a first metal via hole (3), a metal wiring (4), a second metal via hole (5), a reference ground plane (6) and a dielectric substrate (7); the coupling microstrip line (1) is positioned on the first layer of the whole circuit, and the slotting direction is vertical to the extending direction of the coupling microstrip line (1); the two interdigital metal parallel plates (2) on the second layer are respectively connected with the parts, located on the left side of the slot, of the two coupling microstrip lines (1) through first metal through holes (3), and the two interdigital metal parallel plates (2) on the third layer are respectively connected with the parts, located on the right side of the slot, of the two coupling microstrip lines (1) through the first metal through holes (3); one end of each of two metal wirings (4) on the second layer is respectively connected with two interdigital metal parallel plates (2) on the second layer, one end of each of two metal wirings (4) on the third layer is respectively connected with the other end of each of two metal wirings (4) on the second layer through a second metal via (5), the other end of each of two metal wirings (4) on the third layer is respectively connected with one end of each of two metal wirings (4) on the fourth layer through a second metal via (5), the other ends of the two metal wirings (4) on the fourth layer are mutually communicated, and the metal wirings (4) on the second layer to the fourth layer form a vertical folding metal wire; the reference ground plane (6) is the fifth layer of the overall circuit.

2. The miniaturized broadband forward wave directional coupler cell circuit according to claim 1, wherein an overall circuit structure of the miniaturized broadband forward wave directional coupler cell circuit is MM with respect to a plane₁Symmetrical, said plane MM₁Is a symmetrical plane between two coupled microstrip lines; the coupling distance of the slotted coupling microstrip line is kept unchanged.