A novel frequency comparator: applications in frequency meters and in difference clocks for generator frequency error monitors

Abstract

Conventional methods of frequency measurement count the number of cycles in a given time or the number of clock pulses during one or more periods of the unknown signal. This approach is prone to error from the uncertainties associated with the gating of two signals. A novel comparator is described that eliminates this error. The frequency of an unknown signal is compared cycle for cycle with a reference. The comparator has two outputs; one of these indicates which of the two signals is at a lower (or higher), frequency while the other output is a pulse train with a repetition rate equal to the difference of the two frequencies. Applications of the comparator in difference clocks and in frequency meters are presented.