Wave transmission lines and networks – Resonators – Dielectric type
Patent
1993-01-07
1994-10-04
Ham, Seungsook
Wave transmission lines and networks
Resonators
Dielectric type
333235, H01P 710
Patent
active
053529979
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a dielectric resonator structure comprising a resonator made of a dielectric material.
BACKGROUND OF THE INVENTION
Among high-frequency and microwave resonator structures, so-called dielectric resonators have recently become increasingly interesting as they offer e.g. the following advantages over conventional resonator structures: smaller circuit sizes, higher integration level, higher efficiency and lower cost of manufacture. Any element having a simple geometric shape and being made of a material of low dielectric losses and a high relative dielectric constant can be used as a high-Q dielectric resonator. For reasons of the manufacturing technique the dielectric resonator is usually cylindrical, such as a cylindrical disc.
The structure and operation of dielectric resonators are described e.g. in the following articles: Siemens Components XXIV (1989) No. 5, p. 180-183. Journal, September 1986, p. 189-191. Microwave Circuits, Marian W. Pospieszalski, IEEE Transactions on Microwave Theory and Techniques, VOL. MTT-27, No. 3, March 1979, p. 233-238.
The resonance frequency of the dielectric resonator is primarily determined by the dimensions of the resonator element. Another factor affecting the resonance frequency is the surroundings of the resonator. The electric or magnetic field of the resonator and thus the resonance frequency can be intentionally affected by introducing a metal surface or any other conductive surface in the vicinity of the resonator. To adjust the resonance frequency of the dielectric resonator, a common practice is to adjust the distance between the conductive metal surface and the planar surface of the resonator. The adjusting mechanism may be e.g. an adjustment screw attached to the housing surrounding the resonator.
In this kind of adjusting method, however, it is typical that the resonance frequency varies non-linearly as a function of the adjusting distance. Due to the non-linearity and the steepness of the adjustment, it is difficult and requires high precision to accurately adjust the resonance frequency, especially in the upper end of the adjusting range. In addition, the unloaded Q-factor varies as a function of the distance between the conductive surface and the resonator.
A constant Q-factor and more linear frequency adjustment can be obtained within a wider range by replacing the conductive adjustment surface or plate with a dielectric adjustment plate the distance of which from the planar surface of the resonator is adjusted. FIG. 7 in the above-mentioned article [2] shows a so-called double resonator structure as a modification of this solution. In the double resonator structure, two cylindrical dielectric resonator discs are positioned co-axially close to each other so that the distance between their planar surfaces can be adjusted by displacing the discs in the direction of their common axis. Also in this case the adjustment curve is still steep, in addition to which the double resonator structure is larger and more complicated than a conventional structure utilizing an adjustment plate.
SUMMARY 0F THE INVENTION
The object of the invention is to provide a dielectric resonator structure in which the resonance frequency can be adjusted more accurately than was previously possible.
This is achieved by means of the dielectric resonator structure according to the invention, wherein the resonator is supported between two support plates and displaceable at least in one direction between the support plates, at least one of the support plates being made of a dielectric material so that the amount of the dielectric material of the dielectric support plate varies in a direction of displacement of the resonator.
The basic idea of the invention is that the resonance frequency is adjusted by varying the amount of dielectric material in the vicinity of the resonator by moving the resonator in place of the frequency adjuster. In the preferred embodiment of the invention, the resonator disc is attached and supported by means of di
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S. J. Fiedziusko, "Microwave Dielectric Resonators", Microwave Journal, Sep. 1986, pp. 189-198.
M. W. Pospieszalski, "Cylindrical Dielectric Resonators and their Applications in Tem Line Microwave Circuits", IEEE Transactions on Microwave Theory and Techniques, vol. MIT-27, No. 3, Mar. 1979, pp. 233-238.
Gundolf Kuchler, "Ceramic Resonators for Highly Stable Oscillators", Engineering, Siemens Components, XXIV, 1989 No. 5, pp. 180-183.
Ham Seungsook
Nokia Telecommunication Oy
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