Slow switch for bandwidth change in phase-locked loop

摘要

The invention is directed to a phase-locked loop circuit which utilizes a voltage controlled oscillator controlled by a pair of loop filters one of which passes a narrow range of frequencies and the other of which passes a wide range of frequencies. A variable impedance connects the outputs of the filters, with the output of the narrow loop filter connected to the input of the voltage controlled oscillator. Means are provided for controlling the variable impedance so as to smoothly switch control of the voltage controlled oscillator from the wide loop filter to the narrow loop filter for accurate and smooth phase locking.