阅读说明：本技术 一种小型化宽带前向波定向耦合器单元电路 (Miniaturized broadband forward wave directional coupler unit circuit ) 是由 于正永 易鑫 施永荣 钱建波 王志勃 乔琪 丁胜高 张悦 于 2019-09-17 设计创作，主要内容包括：本发明公开一种小型化宽带前向波定向耦合器单元电路。该前向波定向耦合器单元电路共有五层电路结构。开槽的耦合微带线位于整体电路第一层,交指金属平行板位于整体电路第二层和第三层,开槽的耦合微带线和交指金属平行板通过金属过孔连接；垂直折叠金属线从第二层中间位置开始,折叠弯曲至第四层中间位置,层与层之间通过金属过孔连接；第五层为整体电路的参考地。所述五层电路结构的每层金属层之间为衬底介质。5个单元电路的级联,增大了奇偶模累积相位差,在5.5-9GHz频段内实现0.5dB的能量耦合度,耦合相对带宽达48.27％。所述前向波定向耦合器单元电路大大缩小了整体电路尺寸,结构较简单,实用性较强。(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.)

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 comprising a slotted coupling microstrip line, an interdigital metal parallel plate, a metal via hole and a plurality of layers of vertical folding metal wires; the slotted coupling microstrip line is positioned on the first layer of the whole circuit; the interdigital metal parallel plates are respectively positioned on the second layer and the third layer of the whole circuit and are respectively connected with the slotted coupling microstrip line on the first layer through metal via holes to form a series interdigital capacitor; 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 the metal through hole, so that the parallel folding inductor is realized; the fifth layer is a reference ground of the miniaturized broadband forward wave directional coupler unit circuit; and a substrate medium is arranged between each metal layer of the five-layer circuit structure.

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 plane₁And the coupling distance of the symmetrical slotted coupling microstrip lines is kept unchanged.

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) a Defected Ground Structure (DGS) is introduced into a reference ground plane of the coupling microstrip line, and the phase difference between odd and even modes is increased, so that the circuit size is reduced, and energy coupling is realized, 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 five-layer circuit structure including slotted coupled microstrip line, interdigital metal parallel plate, metal via hole and multilayer vertical folded metal wire. The slotted coupling microstrip line is positioned on the first layer of the whole circuit; the interdigital metal parallel plates are respectively positioned on the second layer and the third layer of the whole circuit and are respectively connected with the slotted coupling microstrip line on the first layer through metal via holes to form a series interdigital capacitor; 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 the metal through holes, so that the parallel folding inductor is realized. The fifth layer is the reference ground of the whole circuit. A substrate medium is arranged between each metal layer of the five-layer circuit structure.

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 shows an MM of the miniaturized broadband forward wave directional coupler unit circuit provided by the present invention₁A 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: 1-slotted coupled microstrip line, first layer circuit; 2-interdigital metal parallel plate, first layer vertical folding metal wire and second layer circuit; 3-interdigital metal parallel plate, second layer vertical folding metal wire and third layer circuit; 4-a third layer of vertical folding metal wires and a fourth layer of circuits; 5-global circuit reference ground, fifth layer circuit; MM (Measure and Regulation)₁Is a slotted coupling microstrip line symmetrical plane; LL (LL)₁Is a section plane at the interdigital metal parallel plate.

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 2, the miniaturized wideband forward wave directional coupler unit circuit provided by the present invention has five circuit structures, all of which are made of metal, and a medium is arranged between layers. The microstrip line structure comprises a slotted coupling microstrip line, an interdigital metal parallel plate, a metal through hole and a plurality of layers of vertical folding metal lines. 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 invention₁Is a slotted coupling microstrip line plane of symmetry, LL₁Is a section plane at the interdigital metal parallel plate.

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 is the vertical distribution of the interdigital metal parallel plate and the slotted coupling microstrip line. Coupled microstrip line at the middle point L of the distance unit₁A 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.