JPH01147902A - Transmission line connection device - Google Patents

Abstract

PURPOSE:To reduce the transmission loss by forming the cross section of an outer conductor of a connector as a circular shape at the coaxial line side and forming the connector to be a shape having the shortest distance and the longest distance from the center conductor at the coplaner line side. CONSTITUTION:One end of a connector 101 has an SMA connector 201 connecting to a coaxial line and the other end is connected to a coplaner line where a center conductor 202 and a ground conductor 203 are formed on a ceramic base 206. The shape of cross section of the outer conductor of the connector 101 is circular 103 at one end as the same as the coaxial line and the other side is formed as a shape 104 having a part 105 whose distance with the center conductor 102 is shortest and a part 106 whose distance with the center conductor 102 is longest, and the shape of cross section is varied smoothly from one end to the other. Then the shape of electric line of force is varied continuously from the radial shape into a shape concentrated horizontally, then the transmission loss in the conversion from the coaxial line to the coplaner line is reduced considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a converter between a coaxial line and a coplanar line of a microwave transmission line.

Conventional technology When a microwave circuit includes circuit elements such as transistors, resistors, capacitors, or inductors, the microwave circuit is formed on a ceramic substrate or printed circuit board, and these circuit elements are formed on a flat surface. Accumulate. However, when introducing microwaves into these circuits,
Micro transmission lines are used, but coaxial lines are generally used as transmission lines with no loss.

For this reason, a coaxial transmission line is converted into a transmission line in a microwave integrated circuit by human input to a microcircuit, but the transmission line in a microwave integrated circuit is a microstrip line. For this reason, methods have been proposed for converting transmission lines between coaxial lines and microstrip lines to minimize mismatches caused by the shape of the transmission lines and transmission losses. However, microstrip lines only work on the surface of the substrate because it is necessary to form electrodes on both sides of the substrate, and in some cases it is necessary to form holes called pie holes to connect the electrodes on the back and front surfaces. It has become possible to use coplanar lines, which can be used by simply forming a signal line and a ground electrode.

As coplanar lines come to be used in general microwave integrated circuits, conversion between coplanar lines and coaxial lines becomes necessary. FIG. 3 shows a connection between a coplanar line and a coaxial line in the prior art. In Figure 3, 30
1 is a ground electrode of the coaxial line, 302 is a center conductor of the coaxial line, 303 is a coplanar line, 3 and 04 are ground electrodes of the coplanar line, and 305 is a dielectric substrate on which the coplanar line is formed.

In the conventional connection method shown in FIG. 3, the coaxial line and the coplanar line are directly connected, and the center conductor 302 of the coaxial line is connected to the coplanar line 303, and the ground electrode 301 of the coaxial line is connected to the ground of the coplanar line. It is configured to directly contact electrode 304. In this method, even if great care is taken in connecting the connections, there is a return loss of 0.1 dB to 0.3 dB at 12 GHz, and 0.1 dB at 18 GHz. There was a reflection loss of about 3dB to 0.5dB. The main cause of these losses is thought to be the mismatch between the propagation modes propagating through the respective transmission lines, as shown in FIG.

As shown in Figure 4(a), within the coaxial line, the solid line 40
It has a propagation mode represented by electric lines of force extending radially from the center conductor to the outer electrodes as shown in 1, and magnetic lines of force surrounding the center conductor as shown in broken line 402.

On the other hand, in a coplanar line, lines of electric force as shown at 403 in FIG. be. For this reason, a connection method in which these two transmission lines are brought into direct contact has a large propagation loss because the propagation mode, that is, the shape of the electric lines of force at the connection portion is greatly different.

Problems to be Solved by the Invention The problems to be solved by the present invention are that in the prior art, when connecting a coaxial line and a coplanar line, the central body and the ground conductor are directly connected, so propagation due to mismatching of propagation modes occurs. This is because there are a lot of losses.

Means for Solving the Problems The means for solving the problems according to the present invention is that, in a connector between a coaxial line and a coplanar line of a microwave transmission line, a center conductor and an outer circumferential conductor each having a concentric cross section on one side are In a coaxial line, the distance between the center conductor and the outer conductor in the direction of one center line is such that the distance between the center conductor and the outer conductor in the direction other than the center line is such that the distance between the center conductor and the outer conductor is A coaxial transmission line and a coaxial transmission line using a transmission line connector characterized in that the transmission line has a shape that is the closest to the outer conductor in a direction perpendicular to the direction of the center line, and the farthest distance from the outer conductor in a direction perpendicular to the direction of the center line. This is to connect with the coplanar line.

Function The function of the present invention will be explained using FIG. FIG. 1 shows a transmission line connector according to the present invention, in which 101 is a ground electrode;
(a) is a front view, 102 is a center conductor, (b) is a cross-sectional view of one end, and the coaxial outer conductor 103 is a concentric circle as shown in the figure, and (C) is a cross-sectional view of the other end. It is. As can be seen from FIG. 1, if the cross-sectional structure is the same as that of a coaxial transmission line, the distance from the outer conductor 105 in the direction of one center line of the center conductor as shown in (c)m is the same as that of the center line. It has a shape that is the closest to the outer circumferential conductor 106 in a direction other than the direction , and the farthest distance to the outer circumferential conductor 106 in a direction perpendicular to the direction of the center line.

With such a cross-sectional structure, the lines of electric force are radial as shown at 107 on the coaxial transmission line side, but the lines of electric force are concentrated in the horizontal direction as shown at 108 at the other end. . Therefore, by smoothly changing the cross-sectional shape from the coaxial type 103 to the outer circumferential conductor 104 approaching the center line direction, the lines of electric force 107 are changed into lines of electric force 10B that are continuously concentrated in the horizontal direction.

The electric lines of force 108 concentrated in the horizontal direction are almost similar to the electric lines of force 403 in the coplanar line shown in FIG. By connecting the outer circumferential conductor close to , it is possible to eliminate mismatching of propagation modes and reduce propagation loss.

Embodiment An embodiment of the present invention is shown in FIG. FIG. 2 is a perspective view of an embodiment in which a coaxial SMA connector 201 and a coplanar line 202 formed on a ceramic substrate 206 are connected to the transmission line connector shown in FIG. As shown in the figure, a coaxial SMA connector 201 is connected to a portion 103 at one end of the transmission line connector that has a coaxial cross-sectional shape.
The other outer circumferential conductor 105, which is closer to the horizontal direction, is connected to the ground electrode 203 of the coplanar line.

Note that in this embodiment, the center conductor 102 in the transmission line connector
was fixed to the central shaft with Teflon blocks designated 204 and 205. Also, the length of the transmission line connector is 20
cm.

In order to measure the transmission loss of the transmission line connector,
Two transmission line connectors according to the present invention are connected to both ends of the coplanar line indicated by 02.203, and one coaxial SMA
As a result of measuring the transmission loss from the connector to the other coaxial SMA connector, it is 0 per connection point at 12 GHz.
．． 05~0°15dB, and 0.0 at 18GHz.
The loss was reduced to 15 to 0.25 dB, which is approximately 1/2 compared to the conventional method.

Effects of the Invention By using the transmission line connector according to the present invention, the transmission loss at the connection portion is drastically reduced to half that of the conventional one, and is 0.05 to 0.15 dB per connection point at 12 GHz.
It was 0.15 to 0.25 dB at 8 GHz.

[Brief explanation of the drawing]

FIG. 1(a) is a structural front view of the transmission line connector according to the present invention, FIGS. 1(b) and (c) are cross-sectional views of the end of the transmission line connector, and FIG. 2 is an embodiment of the present invention. FIG. 3 is a perspective view of a conventional connector, and FIGS. 4(a) and 4(b) are cross-sectional views illustrating electric lines of force and magnetic lines of force in a coaxial transmission line and a coplanar line. . 101... Outer conductor, 102... Center conductor, 103
... Coaxial outer conductor, 104 ... Horizontally spaced outer conductor, 107.108 ... Lines of electric force, 201
...Coaxial connector, 202-...Coplanar line, 2
03...Grounding conductor of coplanar line. Name of agent Patent attorney Toshio Nakao Scale 1 base 1 Figure ζ mountain) lθ6 Figure 2 Figure 3 C2

Claims (1)

[Claims] In a connector between a coaxial line and a coplanar line of a microwave transmission line, one cross section is a coaxial line consisting of a concentric center conductor and an outer circumferential conductor, and the other cross section is the center conductor at the distance between the center conductor and the outer circumferential conductor. The distance to the outer circumferential conductor in the direction of one of the conductors' center lines is closest compared to the distance to the outer circumferential conductor in a direction other than the direction of the center line, and the distance to the outer circumferential conductor in the direction perpendicular to the direction of the center line is the closest. A transmission line connector characterized in that the transmission line has a shape with the longest distance.