Dielectric resonator having two planar surfaces with respective

Details Dielectric resonator having two planar surfaces with respective Dielectric resonator having two planar surfaces with respective

1996-06-04

1998-05-05

Pascal, Robert

Wave transmission lines and networks

Resonators

With tuning

3332191, H01P 710

Patent

active

057480605

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/F195/00546, filed Oct. 4, 1995.


BACKGROUND OF THE INVENTION

The invention relates to a dielectric resonator comprising a dielectric resonator disc having two plane surfaces, and a frequency controller comprising an adjustment mechanism and an electrically conductive adjustment plane, which is substantially parallel with one of the planar surfaces of the dielectric resonator disc and movable by means of the adjustment mechanism in the perpendicular direction with respect to the resonator disc for adjusting the resonance frequency by changing the distance between the adjustment plane and that same one of the planar surfaces of the dielectric resonator disc, and an electrically conductive casing.
Recently, so-called dielectric resonators have become more and more interesting in high frequency and microwave range structures, as they provide the following advantages over conventional resonator structures: smaller circuit sizes, higher degree of integration, improved performance and lower manufacturing costs. Any object which has a simple geometric shape, and the material of which exhibits low dielectric losses and a high relative dielectric constant may function as a dielectric resonator having a high Q value. For reasons related to manufacturing technique, a dielectric resonator is usually of a cylindrical shape, such as a cylindrical disc.
The structure and operation of dielectric resonators are disclosed e.g. in the following articles: Siemens Components XXIV (1989) No. 5, p. 180-183. Journal, September 1986, p. 189-189. 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 a dielectric resonator is primarily determined by the dimensions of the resonator body. Another factor that has an effect on the resonance frequency is the environment of the resonator. By bringing a metallic or any other conductive surface to the vicinity of the resonator, it is possible to intentionally affect the electric or magnetic field of the resonator, and thus the resonance frequency. In a typical method for adjusting the resonance frequency of the resonator, the distance of a conductive metallic surface from the planar surface of the resonator is adjusted. One prior art dielectric filter design of this kind is shown in FIG. 1, in which a resonator comprises inductive coupling loops 5 (input and output), a dielectric resonator disc 3 installed in a metal casing 4, supported by a dielectric leg 6, and a frequency adjuster attached to the metal casing 4, comprising an adjustment screw 1 and a metal plane 2. The resonance frequency of the resonator depends on the distance L between the resonator disc 3 and the metal plane 2 in accordance with a graph in FIG. 2.
Alternatively, it is also possible to introduce another dielectric body to the vicinity of the resonator body instead of a conductive adjustment body. One prior art filter design of this kind, based on dielectric plate adjustment is shown in FIG. 3, in which a resonator comprises inductive coupling loops 35 (input and output), a dielectric resonator disc 33 installed in a metal casing 34, supported by a dielectric leg 36, and a frequency adjuster attached to the metal casing 34, comprising an adjustment screw 31 and a metal plane 32. The resonance frequency of the resonator depends on the adjustment distance L between the resonator disc 33 and the metal plane 32 in accordance with a graph in FIG. 4.
As appears from FIGS. 2 and 4, in both adjustment techniques, the resonance frequency varies as a non-linear function of the adjusting distance. Due to this non-linearity and the steep adjustment slope, accurate adjustment of the resonance frequency is difficult and demands great precision, particularly at the extreme ends of the control range. Frequency adjustment is based on a highly accurate mechanical movement, the adjustment slope k also being steep. In principle, the length and thus the accura

REFERENCES:
patent: 4477788 (1984-10-01), Collinet et al.
patent: 4849722 (1989-07-01), Cruchon et al.
Derwent's abstract, No. 94-158338/19, Week 9419, Abstract of SU, 1800523 (BUBNOV P M), 31 Mar. 1989.

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