Abstract: Method and apparatus for determining a generalized harmonic number in a harominic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a harmonic number. The likelihood of error in determining harmonic number is reduced by providing a large separation between local oscillator frequencies that are used in determining harmonic number. The method involves the steps of determining an estimated harmonic number utilizing closely-spaced local oscillator frequencies and then utilizing the estimated harmonic number to compute widely-spaced local oscillator frequencies which are utilized for determining a corrected generalized harmonic number. One variation of the technique is utilized for high harmonic numbers, and another variation of the technique is utilized for low harmonic numbers.

Abstract: An input signal of unknown frequency is applied to a sampler which is driven by a sampling signal of frequency f.sub.O to produce an intermediate signal of frequency f.sub.IF. The sampling frequency f.sub.O varies in response to a randomly, or pseudo-randomly varying signal which in turn causes the signal of frequency f.sub.IF to also vary. f.sub.IF will vary in the same way as f.sub.O, but with a scale factor of .+-. N, where N is the harmonic number. Correlation techniques are used to determine the harmonic number and the sideband to enable calculation of the input frequency. Errors in the determination of the harmonic number and sideband due to frequency modulation of the input signal are reduced, due to the variation imposed on the sampling frequency f.sub.O.