Harmonic frequency synthesizer with adjustable frequency offset

Abstract

Abstract A frequency synthesizer having a comb frequency generator, comb line selection filter, and phase locked loop for filtering out spurious signal components and for offsetting the synthesizer output frequency from the frequency of a signal which is output by the comb line selection filter. A reference signal source generates a reference signal having a reference frequency and outputs the reference signal to the comb frequency generator. The comb frequency generator outputs a plurality of comb spectrum signals having frequencies which are respective integer multiples of the reference frequency. An input mixer connected to the comb frequency generator and to a coarse tuning signal source translates the frequencies of the comb spectrum signals to place one selected signal of the comb spectrum signals within a pass band of the comb line selection filter, which outputs the selected signal to the phase locked loop. The phase locked loop includes a voltage controlled oscillator (VCO) which generates an output signal in response to the selected comb spectrum signal and in response to a feedback signal generated by a single sideband (SSB) mixer circuit receiving a portion of the VCO output signal. A fine tuning signal source is connected to the SSB mixer circuit and provides a fine tuning signal to the SSB mixer to shift the VCO output signal frequency by the amount of the frequency of the fine tuning signal, that amount being less than the frequency spacing of the comb spectrum signals. An output mixer receives the VCO output signal and the coarse tuning signal to shift the frequency of the VCO output signal in a direction opposite to the frequency translation of the comb spectrum signals to establish the desired frequency of the synthesized frequency signal.

Inventors

• 👤 Warren E. Guthrie

Bibliographic Details