JPS5863201A - High frequency circuit device - Google Patents

Abstract

PURPOSE:To ensure the stable working and easy control for a high frequency circuit, by providing an electric wave absorber to the inner side of a metallic upper cover and absorbing the electromagnetic field of an undesired mode that is generated within a housing. CONSTITUTION:A microstrip line 3 is formed on a dielectric substance 2 which is joined to an earth conductor 1. Thus a high frequency cicuit is formed. This circuit is joined to a housing 7 which is provided with a metallic housing 4 and a metallic upper cover 5 containing an electric wave absorber 6 of having (t) thickness adhered to its inner side to absorb the electromagnetic wave generated within the housing. In general, the undesired resonance of the metallic housing does not occur in case when a side of the square metallic housing is equal to the wavelength within a tube of a transmitting signal band (or a handling frequency band) and shorter than the half wavelength. However, the size of the housing is inevitably large with an actual high frequency circuit. As a result, the undesired resonance is produced within the metallic housing. In this connection, the absober 6 is provided to absorb the undesired electromagnetic field generated within the housing 7. Thus the undesired resonance can be easily eliminated for the housing 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency circuit device in which a high-frequency circuit is provided inside a metal casing, and a simple structure that absorbs an electromagnetic field of an unnecessary mode generated inside the casing and stabilizes the circuit operation. The purpose of this is to simplify the adjustment of the circuit.

Generally, a high-frequency circuit in the microwave band is surrounded by a metal casing to eliminate electromagnetic coupling with the outside, eliminate influences from outside the casing, and eliminate electromagnetic radiation from inside. However, depending on the frequency of the signal transmitted through the transmission line and the shape and dimensions of the metal casing,
The design and adjustment of high-frequency circuits was not easy because the metal casing could cause resonance at unnecessary frequencies.

The present invention eliminates the above-mentioned drawbacks, and the practical aspects of the present invention will be explained below with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the present invention.

In the figure, a microstrip line 3 is formed on a dielectric 2 joined to a ground conductor 1, forming a high frequency circuit. This is joined to a casing 7 consisting of a metal surrounding casing 4 and a metal top cover 6 to which a radio wave absorber 6 having a thickness of t is adhered to the inner surface for absorbing electromagnetic waves generated in the casing. ing.

Fig. 2 is an example of a bandpass filter configured with a microstrip line 3'; (,) is a plan view thereof;
(b) is a sectional view thereof.

3.

3 shows the transmission characteristics when the high frequency circuit shown in FIG. 2 is incorporated into the housing 7 shown in FIG. 1, and FIG. 4 shows the transmission characteristics when the high frequency circuit shown in FIG. 2 is installed in the case 7 shown in FIG. The part indicated by the arrow in the figure is the unnecessary resonance that occurs in the metal casing.

Generally, if the dimension of one side of a rectangular metal casing is smaller than half the wavelength of the signal band to be transmitted (or the frequency band handled), unnecessary resonance of the metal casing will not occur, but in actual high-frequency circuits, Usually, the shape of the casing becomes larger. Therefore, in the past, unnecessary resonance as shown in FIG. 4 could occur inside the metal casing, but as shown in FIG. By attaching it to the inner surface of the upper lid 6 of the housing 7, unnecessary electromagnetic fields generated within the housing 7 can be absorbed, and unnecessary resonance of the housing 7 can be easily eliminated.

Note that resonance may occur in the metal housing 7 in various modes of 1°, but unnecessary electromagnetic waves can be easily absorbed by changing the thickness t of the attached radio wave absorber 6. In addition, the radio wave absorbers actually used are generally made of magnetic or dielectric materials, but if carbon powder is mixed with expanded polystyrene, the thickness can be easily increased. In addition, when adjusting the high frequency circuit, the top cover 6 of the metal casing is generally removed, but when the top cover is attached as in the past, unnecessary When resonance occurs, the circuit operation may differ between when the resonance is adjusted and when the top cover is attached. However, in the present invention, even when the top cover is attached, unnecessary resonance does not occur, so that the circuit can be easily adjusted.

Although FIG. 1 shows one embodiment of the present invention, the same effect can be obtained even if a radio wave absorber 6 is attached to a part of the inner surface of the upper cover 6 of the housing 7 as shown in FIG. 6 as another embodiment. be able to.

As described above, the present invention has a simple structure that eliminates unnecessary resonance caused by the metal casing, stabilizes the circuit operation, and facilitates the adjustment of the circuit. Is there something big?

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2(a). (b) is a plan view and a cross-sectional view showing an example of a high-frequency circuit in which a bandpass filter is configured with a microstrip line;
4 and 4 are characteristic diagrams showing examples of transmission characteristics obtained by the present invention i and transmission characteristics of a conventional example, and FIG. 6 is a sectional view of another embodiment of the present invention. 1...--Grounding conductor, 2...Dielectric, 3...
...Microstrip line, 4...Metal side casing, 6...Metal top cover, 6...
...Radio wave absorber, 7...Metal casing. Name of agent Patent attorney Toshio Nakao and 1 other person2 Figure 1 Figure 2 Figure 5

Claims (1)

[Claims] (1) It has a casing consisting of a metal surrounding casing and a top lid that incorporates a high-frequency circuit using a microstrip line, and a radio wave absorber is attached to the inner surface of the metal top lid, and a radio wave absorber is installed inside the casing. A high frequency circuit device characterized in that it is configured to absorb electromagnetic fields in unnecessary modes. (2) A high-frequency circuit device according to claim (1), characterized in that the radio wave absorber is made of a material in which carbon powder is mixed with expanded polystyrene.