CN107275735B

CN107275735B - Novel coaxial microstrip converter

Info

Publication number: CN107275735B
Application number: CN201710445723.6A
Authority: CN
Inventors: 谢小强; 杨超; 杨迎; 穆继超; 赵轩; 佘宇琛
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2017-06-14
Filing date: 2017-06-14
Publication date: 2020-05-01
Anticipated expiration: 2037-06-14
Also published as: CN107275735A

Abstract

The invention discloses a novel coaxial microstrip converter. The converter comprises a cavity, a coaxial line, a transition cavity and a microstrip line. The transition cavity is positioned between the microstrip line and the coaxial line. One end of the microstrip line is grounded, and the other end is an output end. The back metal plate and the medium substrate at the quarter wavelength of the microstrip line from the grounding end are provided with a through hole, and the inner conductor of the coaxial line passes through the transition cavity and the through hole and is connected with the strip conductor of the microstrip line. Because one end of the connection point of the coaxial line and the microstrip line is a short-circuit line with a quarter wavelength, the coaxial inner conductor is ensured to be positioned at the maximum voltage on the microstrip line, namely the position with the strongest electric field, and the transition cavity is used for carrying out echo compensation, thereby avoiding the radiation loss generated by conventional transition and leading the coaxial microstrip converter to have smaller insertion loss and good port standing wave. The coaxial microstrip converter is novel in structure, simple, compact and easy to process, achieves structural innovation of the coaxial microstrip converter, and is suitable for popularization and application in the microwave field.

Description

Novel coaxial microstrip converter

Technical Field

The invention belongs to the technical field of microwave and millimeter wave passive transmission lines, and particularly relates to a transition problem of conversion between different microwave and millimeter wave coaxial lines and micro-strips.

Background

With the continuous development of microwave and millimeter wave technology, microwave and millimeter wave hybrid integrated circuits and monolithic integrated circuits are increasingly used in communication, radar, guidance and other systems. The microstrip line belongs to a planar structure, has the advantages of small volume, light weight, easy batch production, good reliability, low cost and the like compared with a waveguide and a coaxial line with a three-dimensional structure, has the defects of high loss, low Q value and low power capacity, and is a planar transmission line which is most used by a Hybrid Microwave Integrated Circuit (HMIC), a single-product microwave integrated circuit (MMIC) and a multi-chip (MCM) at present.

In the microwave and millimeter wave frequency band, in order to facilitate the test, the antenna feed and the connection between the independent microstrip circuits, the input and output ports of the microstrip circuit are often required to be transited to the coaxial line through a conversion structure. When signals need to be transmitted for a certain distance, the circuit must be converted from a microstrip to a coaxial line so as to reduce transmission loss. Therefore, millimeter wave integrated circuits using microstrip often have an interface with coaxial-microstrip transition. For example, to test the electrical performance of a circuit on a printed circuit board and facilitate connection of the circuit to test equipment, it is often necessary to solder a standard 50 Ω coaxial connector at the output port of the circuit, i.e., the inner conductor of the coaxial connector is soldered to the microstrip and the outer conductor of the coaxial connector is soldered to the ground plane of the microstrip, thus forming a typical coaxial-to-microstrip transition.

The basic requirements for conversion are generally: (1) low standing wave, low insertion loss; (2) a frequency bandwidth of one; (3) is convenient for design and processing. The invention improves the traditional coaxial microstrip converter, changes the connection mode into connection from the lower side of the microstrip line, enables the connection position to be positioned at the position with the strongest electric field of the microstrip line through a quarter short circuit, and carries out echo compensation through the transition cavity, so that the transition between the coaxial microstrip converter and the microstrip converter can obtain good standing wave performance and insertion loss performance, and the innovation of the structure is realized on the design of the coaxial microstrip converter.

Disclosure of Invention

The novel coaxial microstrip converter adopts the following technical scheme:

a coaxial microstrip transducer comprises a cavity, a coaxial line, a transition cavity and a microstrip line. The transition cavity is a cylinder, the radius of the transition cavity is smaller than that of the coaxial line outer conductor, and the transition cavity is directly connected with the lower side (the metal grounding layer) of the microstrip line and the coaxial line.

The connecting area of the microstrip line and the transition cavity is not provided with a metal grounding layer, and a through hole with the size equal to that of the coaxial line inner conductor is arranged on the dielectric substrate at the position.

The inner conductor of the coaxial line passes through the transition cavity and the through hole on the microstrip line dielectric substrate to be connected with the strip conductor of the microstrip line. One end of the microstrip line is provided with a grounding through hole, and the other end is an output end.

The distance from the grounding through hole of the microstrip line to the connecting point of the strip conductor of the microstrip line and the inner conductor of the coaxial line is a quarter wavelength.

Drawings

Fig. 1 is a cross-sectional view of the novel coaxial microstrip transition.

Fig. 2 is a bottom view of the novel coaxial microstrip transducer.

Fig. 3 is a parameter simulation diagram of the novel coaxial microstrip converter S11.

Fig. 4 is a parameter simulation diagram of the novel coaxial microstrip converter S21.

Detailed Description

As shown in fig. 1 and 2, the present novel coaxial microstrip transducer includes: a cavity (9), a coaxial line (3, 5, 6), a transition cavity (8), a microstrip line (1, 2, 10). In the example circuit, the cavity (9) material is duralumin. The dielectric substrate (1) of the microstrip line adopts Rogers RT/duioid 5880, and the thickness of the strip conductor (2) is 0.02mm, and the width of the strip conductor is 0.78 mm. The radius of the inner conductor (3) of the coaxial line is 0.15mm, the radius of the outer conductor (5) of the coaxial line is 0.81mm, and the medium (6) of the coaxial line is polytetrafluoroethylene. The transition cavity (8) is an air coaxial line, the inner diameter of the outer conductor is 0.41mm, and the length of the outer conductor is 0.2 mm. The grounding end of the microstrip line is provided with two grounding through holes (4), and the distance from the grounding through holes to the connecting point of the coaxial line inner conductor (3) and the microstrip line strip conductor (2) is 2 mm.

Simulation result graphs of S11 and S21 obtained by using HFSS simulation software with a coaxial line as port 1 and a microstrip line output as port 2 are shown in fig. 3 and 4. As can be seen, the reflection coefficient of the example circuit is less than 20dB and the insertion loss is less than 0.2dB in the frequency range of 30GHz to 38 GHz.

Claims

1. A coaxial microstrip transducer comprises a microstrip cavity, a coaxial line, a transition air coaxial line, and a microstrip line,

the microstrip line comprises a metal grounding layer, a dielectric substrate and a strip conductor from bottom to top;

the transition air coaxial line comprises an inner conductor, a first outer conductor and air filled between the inner conductor and the first outer conductor;

the coaxial line comprises an inner conductor, a second outer conductor and a medium filled between the inner conductor and the second outer conductor, wherein the radius of the first outer conductor is smaller than that of the second outer conductor;

one end of the transition air coaxial line is connected with the microstrip line, and the other end of the transition air coaxial line is connected with the coaxial line;

the microstrip line is characterized in that a metal grounding layer is not arranged at the connection part of the microstrip line and the transition air coaxial line, and the metal grounding layer outside the connection part of the microstrip line and the transition air coaxial line is connected with a first outer conductor of the transition air coaxial line;

a through hole with the size equal to that of the inner conductor is formed at the joint of the microstrip line and the transition air coaxial line, and the inner conductor penetrates through the through hole and then is connected with the strip conductor of the microstrip line;

one end of the microstrip line is provided with a grounding through hole, and the other end of the microstrip line is an output end; the distance from the grounding through hole of the microstrip line to the inner conductor is a quarter wavelength.