JPS5832321Y2 - Stabilized dielectric resonant circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to the configuration of a dielectric resonant circuit in which the resonant frequency changes little with temperature.

Dielectric resonant circuits, which have recently come to be used in the microwave band, use a dielectric resonator made of a material with low loss and good temperature characteristics, such as TiO2-based ceramics, as an insulator. Microwave integrated circuit (hereinafter referred to as MIC) consisting of a substrate and a strip line formed on its top surface
(abbreviated as )).

As for the shape of the dielectric resonator, a cylindrical or rectangular parallelepiped shape is generally used because it is easy to process and has a high Q value.

The resonant frequency when a dielectric resonator molded into a certain shape and a MIC are coupled depends on variations in material properties, errors during processing, differences in the positional relationship between the strip line and the dielectric resonator, and the housing. The designed value may not always be obtained due to differences in the positional relationship between the wall and the dielectric resonator, etc.

Therefore, there is a need for some mechanism that can continuously change the resonant frequency without changing the shape of the already molded dielectric resonator.

For this purpose, for example, the distance between the top conductive surface of the resonant frequency adjustment body (hereinafter referred to as adjustment body) provided close to the top of the dielectric resonator (hereinafter referred to as the adjustment body) and the top surface of the dielectric resonator may be changed. Mechanisms have been adopted that adjust the resonant frequency by tightening the resonant frequency.

By the way, temperature changes in the resonant frequency of such a resonant circuit are as follows: 1. 2. Temperature changes in the characteristics of the dielectric resonator, that is, frequency changes due to temperature changes in dielectric constant and changes in shape due to thermal expansion; This is the sum of frequency changes caused by changes in the distance between the tip end surface of the adjusting body and the top surface of the dielectric resonator due to thermal expansion of the housing and adjusting body.

If this phenomenon is actively utilized, the frequency changes due to effects 1 and 2 will compensate for each other, making it possible to obtain a resonant circuit in which the resonant frequency changes little with temperature.

Conventionally, a stabilized dielectric resonator based on this principle has a structure in which an adjusting body 11 made of metal is attached to a support body 12 through a screw hole, as shown in FIG. A method has been used in which the material is made of a material with a coefficient of thermal expansion, resulting in temperature changes at appropriate distances.

Therefore, the structure of the circuit becomes complicated, which has the disadvantage of significantly reducing the advantage of the simple structure of the dielectric resonant circuit.

In order to overcome the above-mentioned drawbacks, this device consists of a layered structure of a plurality of materials having different coefficients of thermal expansion, and is attached to the lid of the housing and moved up and down by a screw mechanism. After obtaining the resonant frequency, the structure can be adjusted by selecting the thermal expansion coefficient and thickness of each layer so that the separation distance changes appropriately with respect to temperature changes. The purpose is to obtain a simple stabilized dielectric resonator.

This invention will be described in detail below with reference to embodiments.

FIG. 2 is a diagram for explaining a stabilized dielectric resonant circuit which is an embodiment of this invention.

In the figure, the portion of the adjusting body 21 that protrudes into the internal space of the housing has a coefficient of thermal expansion of ε1. ε2. They are made of a material with ε3, and have a thickness of χ1. χ2. Layer 26 with χ3
, 27.28.

The tip surface of 21 can be coated with a highly conductive metal, or if the layer 26 is made of a highly conductive metal, the metal surface of 26 can be used as is. It is considered a conductive surface.

The adjustment body 21 is attached to the housing cover 20 through a screw hole provided therein, and can be moved up and down by a screw mechanism.

Now, the height of the side part 23 of the casing, that is, the height of the internal space of the casing, is defined as H1, the thickness of the insulator substrate 24, and W on the insulator substrate.
When the height L of the dielectric resonator arranged to be microwave-coupled to the tube line 25 is, the coefficient of thermal expansion of the housing side, the insulator substrate, and the material constituting the dielectric resonator is If ε□, ε, and ε1, then the change in the distance between the conductive surface at the tip of the adjuster and the top surface of the dielectric resonator △D with respect to the temperature change △T
is manifested as follows.

By the way, if the rate of change in frequency f due to change in D is taken as
Rate of change m2 of frequency with respect to temperature due to minute changes in D
is calculated as follows.

On the other hand, let ml be the frequency temperature change rate due to the main temperature change of the dielectric resonator itself.

By making l m 1+ I2 + as small as possible, a resonant circuit whose resonant frequency changes little with temperature can be obtained.

As a concrete example, it is 23 if shown numerically.
, 26.28 is made of aluminum, 25 is made of alumina ceramics, and 22 is made of TlO2 ceramics.
Rough X10'/'C, EL=7X10'/'C.

H-10mm, W=1mm, L=4mm, X 1,022
If +73=4mm and I)=1mm, then by substituting these numerical examples into the formula on the bottom line of page 5, we obtain the following.

Here, 72=ε2×106. The rate of change m2 of the resonant frequency with respect to temperature due to a change in D is obtained by substituting the above equation (11) into the equation on the fifth line of page 6.

If the temperature change rate of the resonant frequency due to a temperature change in the characteristics of the dielectric resonator itself is ml, then the temperature change rate of the resonant frequency of the entire resonant circuit is given by m1+m2, as shown in the following equation.

In order to minimize the resonance frequency temperature change, 1m,
The relationship between I2 and X2 may be determined so that +m21=Q.

In other words, you can choose .

In other words, as the material of 27, the expansion coefficient is ε2X10-6
If you choose the thickness of
It may be determined to satisfy the formula.

Although k9m2 is not constant depending on the resonance frequency and the arrangement of each element constituting the resonance circuit, it is a measurable quantity, and -
As an example, 1m11=3X10-, to=2.5X1
A value of about 0-2 is obtained.

Therefore, equation (1) becomes as follows.

103+(23-ε,)・χ,=±120 f2)
If we solve this for χ2, we get one of the following.

χ+ corresponds to negative ml, and χ− corresponds to positive ml.

The material of 27 is Teflon (ε2 = 120 x 1
0', = 120), χi can be realized, and χ;
=2.3mm.

Also, super invar (ε2 = 0.01X10
'tz = 0.01), it is possible to realize Pe.
．． It becomes 73.

As mentioned above, according to this invention, since the adjusting body itself is composed of a layered structure of materials with different coefficients of thermal expansion,
A stabilized dielectric resonator with an extremely simple configuration can be obtained, and its effects are significant.

In the above explanation, a resonant frequency adjusting body on an inner rod with a constant diameter was used, but as shown in Fig. coefficient is different from that of other materials) 31, 32.
It has a layered structure consisting of 33 parts, and the cross-sectional shape of the threaded part is
It is also possible to adopt a structure in which the shape of the tip is different from that of the conductive surface and the pitch of the threaded portion is small.

Further, in the above description, aluminum is used for the parts 23, 26, and 28, but it is also possible to use copper, brass, etc., which are easy to process.

Teflon was mentioned as a material with a large coefficient of thermal expansion, but
Polyethylene or acrylic resin can also be used.

In addition to super invar, it is also possible to use quartz, alumina, covar, etc. as materials with low expansion coefficients.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional stabilizing dielectric resonant circuit, FIG. 2 is a diagram showing one embodiment of this invention, and FIG. 3 is a diagram showing another embodiment of this invention. In the figure, 20 is a housing lid part, 11.21 is an adjustment body, 1
3.22 is a dielectric resonator, 14.23 is a housing, 15.2
4 is an insulator substrate, 16.25 is a strip line, 26,
Reference numerals 27, 28, 31, 32, and 33 indicate material layers having different coefficients of thermal expansion provided at the tip of the adjustment body.

Claims (1)

[Scope of utility model registration request] A microwave integrated circuit consisting of an insulating substrate and a strip line formed on the insulating substrate, a dielectric resonator placed on the dielectric resonator, a casing containing the former two, and a casing attached to the casing lid, It has a resonant frequency adjusting body that can be moved up and down by a screw mechanism and has a conductive surface at its tip, and the distance between the top surface of the dielectric resonator and the conductive surface at the tip of the resonant frequency adjusting body is determined. In a dielectric resonant circuit in which the resonant frequency is variable by changing the resonant frequency, the resonant frequency adjusting body is composed of a layered structure of multiple types of materials with different coefficients of thermal expansion, and the dielectric resonator and the resonant frequency change depending on the temperature change. A dielectric resonant circuit that compensates for temperature changes in the frequency of a dielectric resonator by slightly changing the separation distance between conductive surfaces at the tips of a resonant frequency adjusting body.