JPH03250901A - Dielectric resonator - Google Patents

Abstract

PURPOSE:To remarkably reduce a change in the resonance frequency due to a temperature change by reversing positive and negative in a temperature coefficient of a specific dielectric constant of a dielectric block and a temperature coefficient of a specific dielectric constant of a dielectric substance of a coupling capacitor and selecting the values of the temperature coefficient so that a change in the resonance frequency due to temperature is corrected. CONSTITUTION:A temperature coefficient of a specific dielectric constant of a dielectric block 1 is selected negative and as the temperature rises, a center frequency f0 at the resonance increases. On the other hand, ceramic capacitors having a positive temperature coefficient of +60ppm/ deg.C are employed for coupling capacitors, 10, 11. Thus, the temperature characteristic of the dielectric block 1 is corrected and a rate of change of the center frequency f0 due to temperature is kept within + or -2ppm/ deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dielectric resonator such as a dielectric filter for use in communication equipment such as a car telephone, a personal radio, a cordless telephone, and the like.

[Prior Art] A 1/4 wavelength distributed constant dielectric resonator and a dielectric filter for use in communication equipment, etc.
It is disclosed in JP-A No. 54102 and the like.

[Problem to be Solved by the Invention] The dielectric resonator constituting the dielectric filter is formed from one end surface 2 of the dielectric block 1 to the other end surface 3, as shown in principle in FIG. It has a resonant hole 4 , an inner conductor film 5 of the resonator hole 4 , an outer conductor film 7 on the outer circumferential surface 6 , and an end surface conductor film 8 . The resonant frequency f of this dielectric resonator is expressed by the following equation.

f-I C/ λ lo-I C/ 4/”
-51--F-t.

where λ0 is the wavelength at resonance, εr is the dielectric block 1
, L is the axial length of the resonator, and C is the speed of light.

The dielectric constant of the dielectric block 1 has temperature dependence, and when the temperature changes, the center frequency changes as shown by Bl and B2 in FIG. That is, the center frequency is +10ppm/
It has a temperature gradient on the order of degrees Celsius, and the center frequency changes by about IMHz in the operating temperature range of -30 to +85 degrees Celsius. Such a change is, of course, undesirable.

Therefore, an object of the present invention is to provide a dielectric resonator or filter that has excellent temperature dependence.

[Means for Solving the Problems] To achieve the above object, the present invention includes a dielectric block having at least one resonance hole, an inner conductor film provided on the wall surface of the resonance hole, and a dielectric block having at least one resonance hole. A dielectric resonator comprising an outer conductor film provided on the outer peripheral surface of a body block, a terminal for connecting to a signal line, and a coupling capacitor connected between the terminal and the inner conductor film. wherein the temperature coefficient of relative permittivity of the dielectric block has one of positive and negative values, and the temperature coefficient of relative permittivity of the dielectric of the coupling capacitor has the other of positive and negative values; The present invention relates to a dielectric resonator characterized in that the resonator formed by the dielectric block, the inner conductor film, and the outer conductor film has a value that corrects changes in the resonant frequency due to temperature.

[Function] The slope of the temperature characteristic line of relative dielectric constant (capacitance) of the coupling capacitor according to the present invention is opposite to that of the dielectric block.

Therefore, for example, if the temperature coefficient of the relative permittivity of a dielectric block has a negative value, as the temperature rises, the relative permittivity of the dielectric block will decrease, and the center frequency of resonance will conversely increase. do. However, since the slope of the temperature characteristic line of the coupling capacitor is opposite, as the temperature rises, the capacitance of the coupling capacitor increases and the center frequency is corrected. Although it is difficult to clearly explain why the resonance center frequency is corrected by the temperature characteristics of the coupling capacitor,
This effect has been confirmed experimentally.

[Example] Next, a dielectric filter according to an example of the present invention will be described with reference to FIGS. 1 to 8.

First and second resonance holes 4a% 4b are provided extending from the first end surface 2 to the second end surface 3 of the dielectric block 1. First and second inner conductor films 5a and 5b are provided on the wall surface of each resonance hole 4a%4b, respectively, and a pair of end surfaces 2
．． An outer conductor film 7 is provided on the outer circumferential surface 6 between the inner conductor films 5a, 5b and the outer conductor film 7, respectively. It is provided.

The inner conductor films 5a, 5b, the outer conductor film 7, and the end face conductor film 8 are made by applying and baking silver paste. Note that there is a first end surface 2 between the two resonance holes 4a and 4b.
A coupling hole 9 extending from the to the second end surface 3 is provided.

The first and second coupling capacitors 10 and 11 respectively inserted into the two resonance holes 4a and 4b are connected to one electrode terminal 12.
．． 13 and the other electrode terminals 14 and 15. First and second terminals 16.17 consisting of external connection leads are connected to one electrode terminal 12.13 of the first and second coupling capacitors 10.11, respectively. The other electrode terminal 14.15 of the first and second coupling capacitors 10.11 is connected to the first and second inner conductor films 5aN5b by a connection conductor 18.19 made of metal particles and solder. ing.

As shown in FIG. 2, the first coupling capacitor 10 includes a cylindrical dielectric ceramic 20 and first and second capacitor electrodes 2.
1.22 and an electrode terminal 12.14 consisting of a metal cap.
Consists of. Note that the second coupling capacitor 11 also has the same structure as the first coupling capacitor 10.

A pair of capacitors 10.11 are interconnected by an insulator 23. Note that a metal shield member 24 is further integrated with the insulator 23. Shield member 24
has a portion that covers a pair of side walls in addition to a portion that covers the upper portion of the coupling hole 9, and is formed in a U-shape in cross section as a whole.

When connecting the completed dielectric filter to an electrical circuit,
The first and second terminals 16 and 17 are connected to a high frequency signal transmission line, and the outer conductor film 7 is connected to ground via the shield member 24.

FIG. 4 shows an isotonic circuit of a dielectric filter. A first resonant circuit consisting of a capacitor C1 and an inductance L1 includes a first inner conductor film 5a of the first resonance hole 4a, an outer conductor film 7 to be grounded, an end face conductor film 8, and a dielectric block between them. A second resonant circuit formed based on 1 and consisting of a capacitor C2 and an inductance L2 includes a second inner conductor film 5b of the second resonance hole 4b, an outer conductor film 7 to be grounded, an end face conductor film 8, and , and the two resonant circuits are coupled by a mutual inductance M. This dielectric filter has filter characteristics as shown in FIG.

By the way, the center frequency fO in this filter characteristic diagram
depends on the resonant frequency f mentioned above, and varies depending on the temperature.
It changes as shown by chain lines Bl and B2 in the figure. That is, the temperature coefficient of the dielectric constant of the dielectric block 1 of this embodiment is negative, and as the temperature rises, the center frequency fO at the time of resonance increases. In addition, the temperature coefficient of the coupling capacitor of the conventional dielectric filter with the characteristics of Bl and B2 in Fig. 7 is oppm/
'c, and the center frequency fO at 20°C is 886 Ml (
It is z.

On the other hand, in this embodiment, the coupling capacitor 10.1
As shown in FIG. 6, a ceramic capacitor having a positive temperature coefficient of +60 ppm/° C. is used as the capacitor. As a result, the temperature characteristics of the dielectric block 1 are corrected, and the seventh
As shown by the solid line At and A2 in the figure, the rate of change in the center frequency fO due to temperature is within plus or minus 2 ppI/'C. In addition, in FIG. 7, two solid lines Al,
A2 and two dashed lines Bl and B2 indicate the width (variation) of the center frequency change range. Coupling capacitor 10.11
The relationship between the temperature characteristics and the center frequency fO at resonance is expressed by the eighth
As shown in the figure, the rate of change of the center frequency fO becomes zero when +601)I)l/''C.

[Modifications] The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(1) The coupling capacitors 10 and 11 can be replaced with columnar ceramic capacitors, plate capacitors, etc. other than the cylindrical ceramic capacitors.

(2) The present invention can also be applied to a multistage dielectric filter having three or more resonance holes and a dielectric resonator having one resonance hole.

(3) A 1/2 wavelength type dielectric resonator can be constructed by omitting the end face conductor film 8.

[Effects of the Invention] As is clear from the above, according to the present invention, changes in resonance frequency due to temperature changes can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a central longitudinal sectional view of a dielectric filter according to an embodiment of the present invention, FIG. 2 is a sectional view showing the first coupling capacitor portion of FIG. 1, and FIG. 3 is a dielectric filter of FIG. 1. 4 is an equivalent circuit diagram of the dielectric filter in FIG. 1, and FIG. 5 is a characteristic diagram of the dielectric filter in FIG. 1. , FIG. 6 is a temperature characteristic diagram of the capacitance of the coupling capacitor shown in FIG. 1, FIG. 7 is a diagram showing changes in center frequency due to temperature of the dielectric filter according to FIG. 1 and the conventional dielectric filter, and FIG. The figure shows the relationship between the temperature characteristics of the coupling capacitor and the rate of change of the center frequency of the dielectric filter, and FIG. 9 is a sectional view showing the principle of the dielectric resonator. 1... Dielectric block, 4a... First resonance hole, 4
b...Second resonance hole, 5a...First inner conductor film, 5
b... Second inner conductor film, 7... Outer conductor film, 9...
Coupling hole, 10... first coupling capacitor, 11...
Second coupling capacitor, 16...first terminal, 17.
...Second terminal. Agent Norihiro Takano Figure 4 Figure 5

Claims (1)

[Scope of Claims] [1] A dielectric block having at least one resonance hole, an inner conductor film provided on the wall surface of the resonance hole, and an outer conductor film provided on the outer peripheral surface of the dielectric block. In a dielectric resonator comprising a conductor film, a terminal for connecting to a signal line, and a coupling capacitor connected between the terminal and the inner conductor film, the relative dielectric constant of the dielectric block is The temperature coefficient has one of positive and negative values, and the temperature coefficient of relative dielectric constant of the dielectric of the coupling capacitor has the other value of positive and negative, and the dielectric block, the inner conductor film, and the outer A dielectric resonator having a value that corrects temperature-induced changes in the resonant frequency of the resonator formed with a conductor film. [2] It has first and second end surfaces and an outer circumferential surface between them, and is provided with first and second resonance holes, and a coupling hole is provided between these. They are provided on the dielectric block and on the walls of the first and second resonance holes, respectively. first and second inner conductor films; outer conductor films provided on the outer peripheral surface of the dielectric block; first and second terminals; the first and second terminals and the first and first and second coupling capacitors connected between the first and second inner conductor films of the second resonance hole, respectively, wherein the ratio of the dielectric blocks is The temperature coefficient of dielectric constant has one of positive and negative values, and the temperature coefficient of relative permittivity of the dielectrics of the first and second coupling capacitors has the other value of positive and negative, and the dielectric A dielectric resonator having a value for correcting a temperature change in a center frequency of a dielectric filter including a block, the first and second inner conductor films, and the outer conductor film.