JP2530021Y2 - Microwave circuit - Google Patents

Description

The present invention relates to a microwave circuit, and more particularly to a microwave circuit having a coplanar structure.

(Prior Art) A distributed line coupling line having a strip line configuration obtained by forming a signal line and a ground conductor on both surfaces of a dielectric plate by a printing technique, which is used as a microwave band signal line, is small and inexpensive. It is widely used in various fields because it has excellent advantages such as easy manufacturing.

FIG. 3 is a sectional view showing the basic structure of a directional coupler of a conventional coplanar microwave circuit. Dielectric constant ε _r
Signal line with width w at symmetrical positions on both sides of the dielectric substrate DE
C1 and C2 are formed, and ground conductors G11 and G12 and G21 and G22 are formed on both sides of the signal lines C1 and C2 at intervals s, respectively.

The characteristic impedance of these signal lines C1 and C2 is dielectric DE
And the dielectric constant ε _r , the width w of the signal line, the distance s between the signal line and the ground conductor, and the like.

(Problems to be Solved by the Invention) In the design of a directional coupler of a conventional coplanar microwave circuit in which a signal line is formed at a symmetric position on both sides of a dielectric substrate as described above, the phase constants of the EVEN mode and the ODD mode ( It is assumed that the effective dielectric constants are equal.

However, in the above-mentioned conventional coplanar microwave circuit, the electric field in the EVEN mode is mainly distributed in the air, and the electric field in the ODD mode is mainly distributed in the dielectric substrate. Therefore, EV
The effective permittivity _{e effe in} the EN mode and the effective permittivity _{effo in the} ODD mode do not match, and the ratio of the effective permittivity does not become 1.

As a result, when a directional coupler is configured using such a structure, there is a problem that the directivity is deteriorated.

Therefore, an object of the present invention is to provide a microwave circuit that can make the ratio of the effective permittivity between the EVEN mode and the ODD mode close to 1.

(Means for Solving the Problems) In order to solve the above-mentioned problems, a microwave circuit according to the present invention includes a signal line formed in parallel on both surfaces of a dielectric substrate and a predetermined distance from the signal line. In the microwave circuit having a coplanar structure having a ground conductor and two signal lines formed in parallel on both surfaces, the signal lines are formed at a predetermined distance from each other in the direction perpendicular to the formation direction with the dielectric substrate interposed therebetween.

(Example) Next, this invention is demonstrated, referring drawings.

FIG. 1 is a sectional view showing an embodiment of the microwave circuit according to the present invention.

In this embodiment, signal lines C1 and C2 having a width w are formed on both surfaces of the dielectric substrate DE, and ground conductors G11, G12 and G21, G22 are formed at positions s away from the signal lines C1 and C2. I have.
Here, the characteristic structure of the present invention is the positional relationship between the signal lines C1 and C2 formed on both surfaces of the dielectric substrate DE.

The signal lines C1 and C2 of the conventional structure shown in FIG.
In contrast to the symmetrical position with respect to DE, in this invention,
A signal line C2 is formed in parallel at a position shifted by d from the center of the signal line C1.

As shown in FIG. 1, in the present invention, the centers of the signal lines formed on both surfaces of the dielectric substrate DE are shifted by d. Therefore, since the distance between the signal line and the ground conductor on the opposite surface changes, the electric field distribution in the EVEN mode and the ODD mode can be different from the conventional structure. That is, in the EVEN mode, W on the upper surface and GND (G
22), the lines of electric force that existed in the air until now mainly exist in the dielectric plate, the effective permittivity increases, and in the ODD mode, the upper and lower W Since the distance is large (from the upper and lower W, the electric lines of force pass through the route of upper W ... → space ... → GND ... → dielectric plate ... → GND ... → air ... → lower W, Until now, the electric lines of force that existed in the attraction plate are now also present in the air, and the effective dielectric constant is low. As a result, the effective permittivity of both modes can be made closer.

As described above, according to the present invention, the effective permittivity of the EVEN mode and the ODD mode can be made close to each other. FIG. 2 shows a plan view of an example in which the present invention is applied to a directional coupler.

In FIG. 2, a signal line C1 as shown by a solid line and ground conductors G11 and G12 are formed at a distance s from the signal line C1 on the surface of the dielectric substrate DE. On the other hand, the dielectric substrate DE
A signal line C2 as shown by a broken line, and ground conductors G21 and G22 are formed at a distance s from the signal line C2 on the back surface of. Both signal lines C1 and C2 are connected at a portion A. Furthermore,
The signal lines C1 and C2 in the coupling portion A are formed in parallel at positions shifted by d from the respective centers.

Therefore, in the configuration shown in FIG.
If the thickness and permittivity of the DE, the width w of the signal line, the deviation d, etc. are appropriately set, the microwave input from the input terminal T1 is distributed to the signal line C2 at the coupling part A, and the microwave input from the output terminals T3 and T4. A distribution output having an appropriate ratio is obtained. Here, a non-reflection terminal is generally formed at the terminal T2.

When a directional coupler having the configuration shown in FIG. 2 was prototyped and tested, the directionality of -16 dB when the deviation d was zero was d = 1 mm.
, A directionality of -27 dB was obtained, and a significant improvement in directionality was confirmed.

(Effects of the Invention) As described above, in this invention, the signal lines formed on both surfaces of the dielectric substrate are shifted by a predetermined distance.
The effective permittivity of the EVEN mode and the ODD mode can be made close to each other, so that the design of the microwave circuit is not only accurate, but also the characteristics are greatly improved when applied to, for example, a directional coupler.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a microwave circuit according to the present invention, FIG. 2 is a plan view showing an example in which the present invention is applied to a directional coupler, and FIG. 3 is a conventional microwave circuit. FIG. C1, C2: Signal line, G11, G12, G21, G22: Ground conductor, DE
... dielectric substrate, T1 to T4 ... terminals.

Claims (1)

(57) [Scope of request for utility model registration] 1. A microwave circuit having a coplanar structure having a signal line formed in parallel on both surfaces of a dielectric substrate and a ground conductor formed at a predetermined distance from the signal line. A microwave circuit, wherein the two signal lines formed are separated by a predetermined distance in a direction perpendicular to the formation direction with the dielectric substrate interposed therebetween.