FREQUENCY ACQUISITION AND LOCKING DETECTION CIRCUIT FOR PHASE LOCK LOOP

摘要

A method and apparatus for providing frequency acquisition and locking detection for a phase lock loop is disclosed. The phase lock loop locks a receiver local oscillator to the frequency and phase of an RF carrier to allow data to be recovered from the RF carrier in the receiver. An analog mixer in the phase lock loop compares the frequency and phase of a receive LO output by a voltage controlled oscillator in the phase lock loop and the received RF carrier. A locking indicator dependent on the result of the comparison indicates whether the phase lock loop is locked. The locking indicator is coupled to a comparator. The comparator generates a pulse to close a switch in order to inject a periodic sweeping signal generated by a free running multi vibrator into the phase lock loop to push the receiver LO into the locking range.