Importance

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Abstract

A microwave antenna for use at a limited number of non-harmonically related frequencies, particularly two, includes a pair of reflectors, a detector diode, and a modulator diode mounted on a waveguide in operative spatial relationships which are compromises of closely occurring multiples of half or quarter wavelengths of the frequencies of interest. More particularly, the reflectors are spaced apart such a compromise distance which results in a low voltage standing wave ratio. The antenna includes a coaxial detector diode holder or sidearm positioned on the waveguide and in communication therewith at a position to provide sharp tuning at one of the frequencies while the detector diode is positioned in a coaxial diode holder at a location operative to sharply tune the other frequency. The modulator diode is positioned in the waveguide a distance from the detector diode holder which is a compromise distance based on in-guide half wavelengths at each of the frequencies. The antenna includes impedance matching structures associated with the aperture of the waveguide, the modulator diode, and the detector diode and holder to thereby increase the efficiency of the antenna. A backshort tuning screw is provided to adjust the effective electrical length of the waveguide.

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First Claim