Phase locked loop frequency synthesizer with fine tuning

摘要

A phase-locked loop frequency synthesizer with fine tuning comprises a controlled oscillator, a divider for dividing signals provided by the oscillator, a comparator for comparing signals derived from the divider with a reference signal and for providing a control signal for the controlled oscillator, a fine tuning circuit for providing a fine tuning control signal, and a pulse generator responsive to the fine tuning control signals for providing one or more control pulses to control the divider. The divider preferably comprises a two modulus divider for dividing by one of two factors for a period dependent upon the number of control pulses provided by the pulse generator, and for dividing by the other of the two factors for the remainder of the time period. The pulse generator preferably comprises a pulse detection and synchronization circuit and a control pulse generator, each connected to the output of the two modulus divider.