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Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference

United States Patent

5,910,710
June 8, 1999
View the Complete Patent at the US Patent & Trademark Office
An electrodeless lamp waveguide structure includes tuned absorbers for spurious RF signals. A lamp waveguide with an integral frequency selective attenuation includes resonant absorbers positioned within the waveguide to absorb spurious out-of-band RF energy. The absorbers have a negligible effect on energy at the selected frequency used to excite plasma in the lamp. In a first embodiment, one or more thin slabs of lossy magnetic material are affixed to the sidewalls of the waveguide at approximately one quarter wavelength of the spurious signal from an end wall of the waveguide. The positioning of the lossy material optimizes absorption of power from the spurious signal. In a second embodiment, one or more thin slabs of lossy magnetic material are used in conjunction with band rejection waveguide filter elements. In a third embodiment, one or more microstrip filter elements are tuned to the frequency of the spurious signal and positioned within the waveguide to couple and absorb the spurious signal's energy. All three embodiments absorb negligible energy at the selected frequency and so do not significantly diminish the energy efficiency of the lamp.
Simpson; James E. (Gaithersburg, MD)
Fusion Lighting, Inc. (Rockville, MD)
08/ 754,858
November 22, 1996
This invention was made with Government support under Contract No. DE-FG01-95EE23796 awarded by the Department of Energy. The Government has certain rights in this invention.