JPS6226201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dielectric resonant circuit which is a microwave band resonant circuit.

This resonant circuit consists of a dielectric resonator made of a material with low loss and good temperature characteristics, such as TiO ₂ ceramic, and a microwave integrated circuit consisting of an insulating substrate and a strip line formed on its top surface. It is made by combining circuits (hereinafter abbreviated as MIC). As dielectric resonators, cylindrical or rectangular parallelepiped ones are generally used because they are easy to process and have a high Q value. The resonant frequency when a dielectric resonator, which is usually molded into a certain shape, is coupled with a MIC depends on the processing accuracy, the difference in the positional relationship between the strip line and the dielectric resonator, and the difference between the housing wall and the dielectric resonator. It was very difficult to obtain the designed value due to the difference in the positional relationship between the two. Therefore, some kind of mechanism is required that allows the resonant frequency to be varied continuously without changing the shape of the already molded dielectric resonator.

Conventionally, as a mechanism for mechanically changing the resonant frequency, a strip line 1 is used as shown in Figure 1.
A mechanism has been used in which a metal plate 15 is provided above a dielectric resonator 13 provided close to the dielectric resonator 13, and the resonant frequency is changed by moving the metal plate up and down. Since such a mechanism is provided within the housing 16, the shape of the housing is necessarily large, which increases the risk of unwanted modes and also increases the temperature of the housing geometry. There were drawbacks such as the change in resonance frequency causing larger fluctuations in the resonant frequency.

The purpose of this invention is to eliminate the above-mentioned drawbacks, and to make it possible to adjust the resonant frequency by changing the volume and position of the conductor, and to make it possible to adjust the resonance frequency by changing the volume and position of the conductor, and to make it possible for the volume and position of the conductor within the gap to change slightly due to thermal expansion caused by temperature changes. It is an object of the present invention to provide a dielectric resonant circuit that can compensate for temperature changes in the frequency of a dielectric resonator by taking advantage of this fact, and can be housed in a small-sized housing.

According to the present invention, there is provided a microwave integrated circuit comprising an insulating substrate and a strip line formed on the upper surface thereof, a dielectric resonator coupled thereto, and an air gap formed by removing a part of the insulating substrate. A conductor with a layered structure made of multiple materials with different coefficients of thermal expansion is inserted into this gap, and by changing the position and volume of this conductor, the resonant frequency can be made variable. A dielectric resonant circuit with characteristics can be obtained.

In the resonator according to the present invention, it is possible to compensate for temperature changes in the frequency of the dielectric resonator by utilizing the fact that the volume and position of the conductor within the gap change slightly due to thermal expansion accompanying temperature changes. It becomes possible to realize a dielectric resonant circuit that is small in size and has good temperature stability.

Hereinafter, the present invention will be explained in detail by way of examples.

FIG. 2 is a diagram for explaining a dielectric resonant circuit which is an embodiment of the present invention. In the same figure, 31 is partially removed to create a gap 34.
A dielectric resonator 33 is formed on the insulator substrate.
is placed on the insulating substrate at a position close to the strip line 32 so as to cover the above-mentioned gap. The conductor 35 partially formed with a threaded portion is fixed through a screw hole provided at the bottom of the casing 36 . A portion of the conductor is inserted into the gap bored in the insulator substrate. By rotating the conductor, the relative position of the casing and the metal body changes, and the position and volume of the part inserted into the gap of the conductor changes, which changes the resonant frequency. .

As is clear from FIG. 2, the height h of the internal space of the casing only needs to be greater than the sum of the height of the dielectric resonator and the thickness of the insulating substrate.

By the way, temperature changes in the resonant frequency of a resonant circuit equipped with the above-mentioned frequency adjustment mechanism are due to minute changes in frequency due to the temperature characteristics of the dielectric resonator and thermal expansion phenomena, resulting in changes in the volume of the conductor inserted into the gap, It appears as an addition of minute changes in frequency due to changes in position. Therefore, if the former minute change is compensated for by the frequency minute change due to the latter cause, a dielectric resonant circuit with good frequency stability can be obtained.

In FIG. 2, a part of the conductor 35 is composed of an adjustment plate 39 made of a material having a different coefficient of thermal expansion from that of the conductor body. Now, if the conductor and the side part of the casing are made of a material with a coefficient of thermal expansion γ ₀ , and the adjustment plate 39 is made of a material with a coefficient of thermal expansion γ, then γ>γ _0.
As the temperature rises, the volume of the conductive portion inserted into the gap increases. When γ<γ ₀ , the opposite trend occurs. Depending on whether the temperature coefficient of the dielectric resonator is positive or negative and the magnitude of the absolute value, a material with an appropriate coefficient of thermal expansion is selected as the material for the adjustment plate, and the thickness of the adjustment plate is selected. Combinations can be obtained that compensate for temperature variations in the resonator.

As explained above, according to the present invention, it is possible to obtain a dielectric resonator with a small shape, and the material of the conductor, conductor support, or casing has an appropriate coefficient of thermal expansion. By making this selection, it is possible to obtain a dielectric resonator with good frequency stability against temperature changes, which is highly effective.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional resonant frequency adjustment mechanism, and 11 is an insulating substrate. FIG. 2 is a diagram showing an embodiment of the first aspect of the present invention.

Claims (1)

[Claims] 1. A microwave integrated circuit consisting of an insulating substrate and a strip line formed on its upper surface, a dielectric resonator coupled thereto, a gap formed by removing a part of the insulating substrate, and this gap. It has a conductor with a layered structure of multiple types of materials with different coefficients of thermal expansion inserted into the interior, and the position of this conductor,
A dielectric resonant circuit that is characterized by making the resonant frequency variable by changing its volume.