DEVICE AND METHOD FOR DETECTING DELAY TROUBLE FOR PHASE LOCK LOOP CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a device and a method for detecting a delay trouble of a phase lock loop circuit. SOLUTION: A frequency impulse is impressed as a reference clock signal to an examined phase lock loop circuit 52, and a wave form of a signal output from the circuit 52 is converted into an analytical signal to estimate an instantaneous phase thereof. A linear phase is estimated based on the estimated instantaneous phase, and the estimated linear phase is removed from the estimated instantaneous phase to find a variation term of the instantaneous phase. A delay time is measured based on the term of the instantaneous phase. A time interval when the phase lock loop circuit 52 stays in an oscillation frequency condition is compared with a time interval when the loop 52 in the absence of a delay trouble stays in an oscillation frequency condition to detect the delay trouble.