Method for eliminating subharmonic false locking in sampler and frequency multiplier based source locking systems

摘要

A method for eliminating subharmonic false locking in a sampler and frequency multiplier phase-locked-loop source locking system comprising the modification of a prior known algorithm for determining the frequency of the first local oscillator used for controlling the sampling of the output of a source voltage controlled oscillator. The frequency of the first local oscillator is determined using prior algorithms for determining the lowest usable harmonic number H and the highest usable first oscillator frequency which will maximize sampler efficiency and minimize local oscillator phase noise due to frequency multiplication. Thereater, the harmonic number H as thus determined is modified depending upon whether when divided by a multiplication factor M, where M is the factor by which the frequency of the VCO is multiplied, the remainder thereof is equal to 1/M, 2/M or zero. If the remainder of the division step is zero, then H is increased by one. If the remainder of the division step is equal to 2/M, then H is increased by two. If the remainder of the division step is equal to 1/M, then the magnitude of H as initially calculated is not adjusted. After H has been calculated and, if necessary, adjusted as described above, it is then used to calculate the first local oscillator frequency using the remaining steps in the prior known algorithm.