JPS61167202A - Dielectric resonator - Google Patents

Abstract

PURPOSE:To adjust the resonance frequency over a wide range without reducing no load Q by inserting a tuning unit made of a dielectric in a way possible for taking-in and out to a hollow of a hollow cylindrical dielectric resonance element. CONSTITUTION:The hollow cylindrical tuning unit 28 made of a dielectric material having a high dielectric constant such as a ceramic is inserted to the hollow part of the hollow cylindrical dielectric resonator element 26. The outer diameter of the unit 28 is made slightly smaller than the inner diameter of the hollow part of the resonator element 26. Thus, the unit 28 is made possible in a taking-in and out way toward the arrow without contacting the inner circumferential face of the hollow part of the resonator element 26. Further, a supporting shaft 30 made of a dielectric material having a low dielectric constant is inserted to the hollow part. Since no metallic screw is used, the reduction in the no load Q due to concentrated current is avoided. Thus, the resonance frequency is adjusted over a wide range.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to dielectric resonators, particularly TEo.

The present invention relates to a structure for adjusting the resonant frequency of a dielectric resonator using the S mode or its modified mode.

(Prior art) An example of the prior art is Utility Model Application No. 57-122909.
Disclosed in the issue. In this conventional technology, a dielectric material is supported in a metal case to realize a TEOI6 mode dielectric resonator, and a screw is attached to the metal case, and the screw is moved up and down to bring it closer to the dielectric resonator element. Alternatively, the resonant frequency is adjusted by moving it away. For example, the closer a metal screw is to its dielectric resonator element, the higher the resonant frequency will be.

(Problems to be Solved by the Invention) In the conventional technology using metal screws, the adjustable range of the resonant frequency is narrow, and if the resonant frequency is fo and the amount of change in frequency is ΔfO, the ratio ΔfO/fo is 0. .2% or less (Δfo/fo≦0.2%). This makes the change ΔfO thicker (then, no-load Q (
This is because the decrease in Qo) is significant, and becomes ・miゝχ ΔQ o /Q o ≧ 10%.

Therefore, the main object of the present invention is to provide a dielectric resonator whose resonant frequency can be adjusted over a wider range without reducing Qo.

(Means for Solving the Problems) The present invention provides a TE015 or its modified mode in which a tuning unit made of a dielectric material is inserted into and taken out from a hollow part of a hollow cylindrical dielectric resonator element. It is a dielectric resonator that uses .

(Operation) A tuning unit made of a dielectric changes the actual gh dielectric constant (ε) of the dielectric resonator element, thereby changing the resonant frequency based on perturbation theory.

(Effects of the Invention) According to the present invention, since a metal wire is not used as in the conventional case, that is, a tuning unit made of a dielectric material is used, so there is no reduction in QO due to current concentration.

Therefore, the rate of change of the resonant frequency can also be increased compared to the prior art.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Example) FIG. 1 is an illustrative cross-sectional view showing one embodiment of the present invention.

The dielectric resonator 10 includes a hollow cylindrical case I2 made of a dielectric material such as ceramic. A bottom plate 14 and a lid plate 16 made of ceramic material are similarly fixed to the lower and upper ends of the ceramic case 12. Note that these cases 12. Bottom plate 14 and lid plate 16
is made of a dielectric material with a relatively low dielectric constant, and a through hole is formed in each of the bottom plate 14 and the cover plate 16 approximately at the center thereof. Electrodes 18, 20, and 22 made of a metal material such as silver are formed on the side surface of the cylindrical case 12, the entire surface of the bottom plate 14, and the entire surface of the lid plate 16, respectively. These electrodes 18, 20 and 22 thus form a current path or external electrode.

Inside the case 12, a cylindrical support base 24 made of a low dielectric constant material is attached to the bottom plate 14 at approximately the center thereof. A hollow cylindrical dielectric resonator element 26 made of a dielectric material with a high dielectric constant, such as ceramic, is fixed onto the support base 24 . Therefore, the dielectric resonator element 26 is fixedly held within the external electrode, and the dielectric resonator 10 that utilizes the TEo+t mode is configured as a whole.

A hollow cylindrical tuning unit 28 similarly made of a dielectric material with a high dielectric constant such as ceramic is inserted into the hollow portion of the hollow cylindrical dielectric resonator element 26 . The outer diameter of this tuning unit 28 is made slightly smaller than the inner diameter of the hollow part of the dielectric resonator element 26, so that the tuning unit 28 can come into contact with the inner peripheral surface of the hollow part of the dielectric resonator element 26. It is possible to move in the direction of the arrow. A support shaft 30 made of a dielectric material with a relatively low dielectric constant, such as ceramic, is inserted into the hollow portion of the tuning unit 28, and the support shaft 30 and the tuning unit 28 are fixed at that portion. Therefore, tuning unit 28
In order to displace the support shaft 30 in the direction of the arrow, it is sufficient to raise and lower the support shaft 30 in that direction. The lower end and upper end of this support shaft 30 are provided with bushings 32a made of a low dielectric constant resin material such as Teflon (trade name), respectively, in the through hole of the bottom plate 14 and the through hole of the cover plate 16. and 32b, it is positioned and supported so that it can move smoothly in the direction of the arrow.

Such a dielectric resonator 10 is housed in a metal case 34 made of a metal material such as aluminum,
Each electrode 18, 20 and 22 is electrically connected and mechanically fixed to the inner surface of its metal case 34, for example by brazing. This metal case 34
Like the dielectric case 12, the case 34 includes a hollow cylindrical case 34, and a bottom plate 36 and a cover plate 38 attached to the lower and upper ends of the case 34. A protrusion 40 is formed on the bottom plate 36 so as to protrude downward, and the lower end of the support shaft 30 is inserted into the space formed by the protrusion 40 . Therefore, the inner diameter of this protrusion 40 is selected to be slightly larger than the outer diameter of the support shaft 30. Further, a protrusion 42 is formed on the cover plate 38 so as to protrude upward. This protrusion 42
, a columnar space 42a is formed, and this space 4
The upper end of the support shaft 30 is inserted into 2a.

In the space 42a formed by the protrusion 42,
The upper end of the support shaft 30 is fixed to the lower end of a tuning screw 44 made of brass or the like. The tuning screw 44 has a male threaded portion (not shown) that can be screwed into a female threaded portion (not shown) formed on the inner wall of the protrusion 42 . For this purpose, by inserting a jig (not shown) such as a screwdriver into the groove 44a formed at the upper end of the tuning screw 44 and turning it, the tuning screw 44 and therefore the support shaft 30 are displaced in the direction of the arrow. After all, tuning unit 2
8 can be displaced in the direction of the arrow in the hollow portion of the dielectric resonator element 26. After the tuning screw 44 is displaced in this way and the resonance frequency fO is adjusted appropriately, the tuning screw 44 is fixed by a fixing screw 46 formed on the side surface of the protrusion 42.

Next, it will be explained why the resonance frequency fo can be changed in such a structure. FIG. 2 shows the electric field distribution of the dielectric resonator in a state where the tuning unit 28 is not inserted. As can be seen from FIG. 2, the electric field strength is relatively weak in the hollow part of the dielectric resonator element 26 into which the tuning unit 28 is inserted, so that even if the tuning unit 28 is inserted there, such a The electric field distribution is hardly disturbed. As described above, assuming that the electromagnetic field inside the dielectric resonator hardly changes in its distribution or intensity, the following perturbation equation is obtained.

Δfo: change in fo, Wt: time average of total energy within the resonator, Δε: change in effective dielectric constant, P: electric field strength.

As can be seen from this perturbation equation, by displacing the tuning unit 28, the effective dielectric constant ε at each position changes to produce Δε, thereby changing the resonant frequency fo.

In such a dielectric resonator 10, FIG. 3 shows how the resonance frequencies fo and Qo change when the tuning unit 28 is displaced.

In FIG. 3, the distance Z (mm) shown on the horizontal axis indicates the distance from the axial midpoint O of the dielectric resonator element 26 to the axial midpoint P of the tuning unit 28. As can be seen from FIG. 3, according to the embodiment in FIG. 1, when the central resonant frequency fO is set to -950 MHz, even if fo is changed by Δfo/fo=2%, the change in QO is as follows.
ΔQo/Qo=-2.1%. As described above, according to this embodiment, the frequency adjustment range Δ
f.

/f o can be expanded by a factor of 1 without significantly reducing QO.

In addition, in the above-mentioned embodiment, the dielectric case 12° and the bottom plate 14
and electrodes 18, 20 and 2 using the lid plate 16.
2 was formed to constitute an external electrode.

However, this is to approximate the change in the coefficient of linear expansion of the external electrode to that of the dielectric resonator element, thereby minimizing the influence of the coefficient of linear expansion. Therefore, if appropriate correction means are used, the external electrodes may be made entirely of metal.

Furthermore, in addition to the case where the dielectric resonator element 26 is held in an external electrode, the present invention can also be used when the dielectric resonator element 26 is directly supported on the mounting substrate.

In such a case, a conductive pattern formed on the mounting substrate can be used as the external electrode.

Furthermore, in the embodiment shown in FIG. 1, the dielectric resonator is configured as a cylinder or cylinder as a whole, and a TEo+s mode dielectric resonator is configured. However, a hollow angular dielectric resonator element or case may also be used. In this case, the mode would be a variant of TEo+6.

[Brief explanation of the drawing]

FIG. 1 is an illustrative cross-sectional view showing one embodiment of the present invention. FIG. 2 is a diagram showing the electric field distribution with no tuning unit inserted. FIG. 3 is a graph showing changes in fo and Qo with respect to the displacement of the tuning unit, and the horizontal axis shows the distance Z.
(mm) and the vertical axis represents the resonance frequency f. and Qo, respectively. In the figure, 18, 20 and 22 are electrodes, 26 is a dielectric resonator element, 28 is a tuning unit, 30 is a support shaft, 44 is a tuning screw, and 46 is a fixing screw. Patent applicant Murata Manufacturing Co., Ltd. Agent Patent attorney Yama 1) Yoshito (and 1 other person) Figure 1 2 (J 25 Figure 3 Salmon Z (mm)

Claims (1)

[Scope of Claims] 1. an external electrode, a hollow cylindrical dielectric resonator element fixedly held in relation to the external electrode, and a hollow cylindrical dielectric resonator element inserted into and removably inserted into the hollow part of the dielectric resonator element. including a tuning unit made of a dielectric material.
dielectric resonator. 2. Claim 1, comprising means for displacing the tuning unit in the axial direction of the dielectric resonator element.
Dielectric resonator as described in section.