Reference frequency generation for split-comb frequency synthesizer

摘要

A frequency synthesizing apparatus of the closed-loop design employing a first frequency mixing means to provide a continuous constant increment frequency coverage over a given output signal frequency range. The first frequency mixing means is responsive to the output signal and a first reference signal to provide a first difference signal both when the output signal frequency is higher than and lower than the first reference signal frequency. A frequency comparison means is responsive to the first difference signal and to an input signal, the input signal being continuously variable over a given input frequency range, to provide a first error signal for controlling the output frequency and stabilizing the closed loop. The first reference signal is comprising of a plurality of predetermined, selectable frequencies provided by a phase-locked loop employing a second frequency mixing means. The second frequency mixing means is responsive to the first reference signal and a plurality of predetermined, selectable second reference signals to provide a second difference frequency. Phase comparison means responsive to the second difference frequency and to a third reference signal provides a second error signal to control the frequency of the first reference signal and to lock the phase-locked loop when the frequency of the first reference signal frequency is either the sum of the second and third reference signal frequencies or the difference between the second and third reference signal frequencies.