FREQUENCY OSCILLATOR, PERIOD ERROR DETECTOR, FILTER, SIGNAL DECIDING DEVICE AND DOPPLER VELOCITY METER USING THEM

摘要

PURPOSE:To avoid the influence of dropout or noise to the utmost by resetting and stopping a phase comparator in matching with an error checking signal. CONSTITUTION:A loop open/close switch 202 is open by the error checking signal C at a high level outputted from an error checking circuit on the occurrence of a signal error and a frequency divider 205 and a phase comparator 201 are reset and stopped simultaneously. When the input signal is restored and an error signal goes to a low level, the switch 202 is closed and the frequency divider 205 and the phase comparator 201 are operated simultaneously. A frequency divider 204 keeps frequency division to an output B from a voltage controlled oscillator 203 and it is extracted as an output signal. Since the phase comparator 201 is reset and stopped in matching with the error checking signal, the phase is not measured when the loop is open and phase comparison is started newly independently of the preceding information when the loop is closed again.