Wave transmission lines and networks – Resonators – Dielectric type
Patent
1994-11-30
1998-02-03
Lee, Benny
Wave transmission lines and networks
Resonators
Dielectric type
333227, 333229, 333234, 333231, H01P 700, H01P 710
Patent
active
057149208
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a cavity resonator and dielectric and cavity thereof for use in high frequency signal source and signal processing systems, and also to a method for producing such cavity resonator. The invention has particular, although not exclusive, utility in such systems which operate in the microwave frequency band microwave resonator.
FIELD OF THE INVENTION
Modern radar and telecommunications systems require high frequency signal sources and signal processing systems with stringent performance requirements and extremely good spectral purity.
Thus, there is a need for signal processing systems and signal sources with ever increasing spectral purity, stability and power-handling requirements.
Resonators by their nature provide discrimination of wanted signals from unwanted signals. The purity and stability of the signals produced is directly linked to the resonator used as the frequency determining device and is dependent upon its Q-factor, power handling ability and its immunity to vibrational and temperature related effects.
It is known that a piece of dielectric material has self-resonant modes in the electromagnetic spectrum that are determined by its dielectric constant and physical dimensions. The spectral properties of a given mode in a piece of dielectric material are determined by the intrinsic properties of the dielectric material, its geometric shape, the radiation pattern of the mode and the properties and dimensions of the materials surrounding or near the dielectric.
Prior art resonators have traditionally relied on metallic cavities containing no dielectric material, or on metallic cavities containing a dielectric material which were limited in Q-factor by the properties of the metallic cavity and hence were operated at cryogenic temperatures in order to obtain a better Q-factor. However, to maintain cryogenic temperatures requires equipment which is cumbersome and difficult to incorporate into a portable or compact apparatus.
SUMMARY OF THE INVENTION
The present invention provides a microwave resonator operable at or near ambient temperatures whilst offering improved Q-factor over existing prior art resonators. In accordance with one aspect of the present invention there is provided a dielectric for a cavity resonator comprising a cylindrical portion to substantially confine electromagnetic energy therein and opposing axial ends particularly shaped to be fixedly disposed centrally within the cavity of the resonator.
Preferably the dielectric is formed of pure sapphire. Preferably, the dielectric has a diameter and a height determined by solving Maxwell's equations for a prescribed material intended to operate in a prescribed mode at a prescribed frequency, at a prescribed temperature.
In accordance with another aspect of the present invention, there is provided a cavity for a cavity resonator, including: a cylindrical wall; a pair of opposing axial ends; and a plurality of ports, at least one port being for delivering electromagnetic energy thereto and at least one other port being for receiving electromagnetic energy therefrom; wherein the opposing axial ends are particularly shaped to fixedly engage the opposing axial ends of a dielectric as defined in the preceding aspect of the invention and dispose the dielectric centrally therein.
In accordance with a further aspect of the present invention, there is provided a method for producing a cavity resonator, the method including the steps of material of predetermined size and placing same in a cavity to produce a microwave resonator; piece corresponding to the desired operating mode at the particular temperature; by scaling from the first piece of dielectric material according to the ratio between the initial and desired output frequencies; and first mentioned cavity but varying the diameter and/or height of the further cavity to compensate for manufacturing inaccuracies in the second piece so as to obtain an output frequency closer to the desired output frequency; and resonator operating in the desired mode and at
REFERENCES:
patent: 4992763 (1991-02-01), Bert et al.
patent: 5200721 (1993-04-01), Mansour
1991 IEEE--Resonant Frequencies of Higher Order Modes In Cylindrical Anisotropic Dielectric Resonators by Michael E. Tobar and Anghony G. Mann, Department of Physics, University of Western Australia, pp. 143-146.
1990 Elsevier Science Publishers B.V. (North Holland)--A Very High Stability Sapphire Loaded Superconducting Cavity Oscilator by A.J. Giles, A.G. Mann, S.K. Jones, D.G. Blair and M.J. Buckingham, Department of Physics, University of Western Australia, pp. 145-146.
IEE Proc., vol. 129, Pt. H, No. 4, Aug. 1982--Whispering-Gallery Modes of Dielectric Resonators by C. Vedrenne and Prof. J. Arnaud, pp. 183-187.
1992 IEEE Frequency Control Symposium--Microwave Frequency Discriminator With a Cooled Sapphire Resonator for Ultra-Low Phase Noise by David G. Santiago and G. John Dick, California Institute of Technology, pp. 176-182.
High-QT.E. Stabilised Sapphire Microwave Resonators and Low Noise Oscillators by J.H. Searls, S. Edwards, E.N. Ivanov, M.E. Tobar, R. Woode, Dept. of Physics, University of Western Australia.
Cryogenic Sapphire Microwave Resonator-Oscillator with Exceptional Stability by A.N. Luiten, A.G. Mann and D.G. Blair.
Low Noise, Microwave Siganl Generation Using Cryogenic, Sapphire Dielectric Resonators: An Update by M.M. Driscoll and R.W. Weinert.
A Low-Noise X-Band Gunn Oscillator Using a Sapphire Dielectric Resonator by Sergey N. Bun'kov, Vladimir I. Konstantinov, and Vladimir L. Masalov.
1993 IEEE International Frequency Control Symposium--Closed Loop Tests of the NASA Sapphire Phase Stabilizer by David G. Santiago and G. John Dick, Jul. 1993, pp. 774-778.
1990 IEEE Transactions on Ultrasonics, Ferroelectrics, and Ferequency Control, vol. 37, No. 5, Sep. 1990. Measurement and Analysis of a Microwave Oscillator Stabilized by a Sapphire Dielectric Ring Resonator for Ultra-Low Noise by G. John Dick and Jon Saunders, pp. 339-346.
Blair David Gerald
Edwards Simon John
Ivanov Eugene Nikolay
Searls Jesse Hyuck
Tobar Michael Edmund
Gambino Darios
Lee Benny
Poseidon Scientific Instruments Pty Ltd.
The University of Western Australia
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