Dielectric resonator having adjustment plates movable with respe

Details Dielectric resonator having adjustment plates movable with respe Dielectric resonator having adjustment plates movable with respe

1996-06-04

1997-12-30

Pascal, Robert

Wave transmission lines and networks

Resonators

With tuning

3332191, H01P 710

Patent

active

057035482

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/FI95/00545, filed Oct. 4. 1995.


BACKGROUND OF THE INVENTION

The invention relates to a dielectric resonator comprising a dielectric resonator disc, a frequency controller comprising an adjustment mechanism and a dielectric adjustment plane, which is substantially parallel with the 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, 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 some 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. Alternatively, it is also possible to bring 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. 1, in which a resonator comprises inductive coupling loops 5 (input and output), a dielectric resonator disc 3 installed in a metal casing 4, and supported by a dielectric leg 6, and a frequency controller attached to the metal casing 4, comprising an adjustment screw 1 and a dielectric adjustment plane 2. The resonance frequency of the resonator depends on the adjustment distance L in accordance with a graph shown in FIG. 2.
As appears from FIG. 2, the resonance frequency varies as a non-linear function of the adjusting distance. Due to this non-linearity and the steep slope of adjustment, 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 slope of adjustment k also being steep. In principle, the length and thus the accuracy of the adjusting movement may be increased by reducing the size of the metallic or dielectric adjustment plane. Due to the non-linearity of the above-mentioned adjusting techniques, however, the achieved advantage is small, since the portion of the adjusting curve which is too steep or too flat either at the beginning or at the end of the adjusting movement can not be used. When the resonance frequency becomes higher, e.g. to the range 1500-2000 MHz or higher, the dimensions of the basic elements of the dielectric filter, such as the dimensions of the resonator body or the adjustment mechanism are reduced even more. As a result, adjusting the resonance frequency of a dielectric resonator with prior art solutions sets very high demands on the frequency adjustment mechanism, whi

REFERENCES:
patent: 4477788 (1984-10-01), Collinet et al.
patent: 4565979 (1986-01-01), Fiedziuszko
patent: 4849722 (1989-07-01), Cruchon et al.
patent: 5315274 (1994-05-01), Sarkka

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