A programmable oscillator is a frequency synthesizer with an output phase that tracks an arbitrary function. An offset, phase-locked loop circuit is used in combination with an error control feedback loop to precisely control the output phase of the oscillator.

To down-convert the received signal, several stages of mixing may be employed with the compensation for the time-base distortion of the carrier occurring at any one of those stages. In the Goldstone Solar System Radar (GSSR), the compensation occurs in the mixing from an intermediate frequency (IF), whose value is dependent on the station and band, to a common IF used in the final stage of down-conversion to baseband. The programmable oscillator (PO) is used in the final stage of down-conversion to generate the IF, along with a time-varying phase component that matches the time-base distortion of the carrier, thus removing it from the final down-converted signal.

This work was done by Kevin J. Quirk, Ferze D. Patawaran, Danh H. Nguyen, and Clement G. Lee of Caltech and Huy Nguyen for NASA’s Jet Propulsion Laboratory. NPO-47657

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Programmable Oscillator

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This article first appeared in the October, 2011 issue of NASA Tech Briefs Magazine.

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