Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Distributed parameter resonator-type magnetron
Reexamination Certificate
1997-03-17
2001-07-10
Lee, Benny T. (Department: 2817)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Distributed parameter resonator-type magnetron
C315S039570, C315S039590, C315S005530, C315S005460, C333S235000, C331S090000
Reexamination Certificate
active
06259208
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to magnetron oscillators, and more particularly to optical techniques by which a magnetron oscillator can be frequency tuned.
BACKGROUND OF THE INVENTION
Mechanically tuned magnetrons are widely available, but they suffer from two distinct disadvantages. This type of magnetron can provide only slow frequency tuning, and requires that moving parts penetrate the vacuum envelope of the magnetron, which has an impact on the reliability of the device.
Mechanically tuned magnetron oscillators are typically one of two types, the plunger-tuned magnetron and the coaxial magnetron. The plunger-tuned magnetron uses a plunger to which metallic probes are attached, and inserts and retracts probes from each of the magnetron's resonant cavities in order to perturb their resonant frequencies.
FIG. 1
illustrates an exemplary plunger-tuned magnetron, using a “crown-of-thorns” tuning scheme, in cross-section. The anode block encircles the cathode, and a number of resonant cavities are formed in the end spaces between the anode block and the cathode. The inductive tuning elements, supported on a tuner frame, are inserted into and retracted from the resonant cavities on bellows, in order to change the cavities' inductance and hence their resonant frequencies.
The coaxial magnetron places the magnetron anode block inside a coaxial resonant cavity, whose dimensions are mechanically changed to tune the frequency.
Both types of magnetrons suffer from all the disadvantages inherent in mechanically tuned mechanisms, i.e., they are slow and require that moving parts penetrate the vacuum envelope.
It would therefore represent an advance in the art to provide an electronic tuning mechanism for a magnetron oscillator so that the frequency can be varied more rapidly than is possible with mechanical tuning.
It would further be advantageous to provide a magnetron oscillator wherein device construction is simplified with no moving parts penetrating the vacuum envelope, thereby lowering the fabrication cost and providing increased reliability.
SUMMARY OF THE INVENTION
These and other advantages and advances are provided by an optically tuned magnetron oscillator. The magnetron employs materials whose electrodynamic properties are altered by the absorption of light. A probe constructed from a leaky dielectric light guide coated with a photoconductive material is inserted into each of the magnetron's cavities. When light is injected into the light guide, it leaks into the coating where it is absorbed as it creates free charge carriers, whose presence alters the reflective characteristics of the coating, thereby perturbing the resonant frequency of the cavity. The frequency can be controlled by varying the amount of light injected into each of the optical probes. When no light is present, the resonant frequency of the magnetron cavity will be at one extreme of its operating band; when the light is at full intensity, the change in the properties of the probe will be maximum as will be the change in the resonant frequency. The invention provides an electronic means of tuning a magnetron, whereas existing tunable magnetrons are tuned by mechanical structures.
REFERENCES:
patent: 4282499 (1981-08-01), De Fonzo
patent: 5099214 (1992-03-01), Rosen et al.
patent: 2020088 (1992-11-01), None
Collins David W.
Lee Benny T.
Lenzen, Jr. Glenn H.
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