SIGNAL DETECTING CIRCUIT FOR DETECTING A SIGNAL SPECIFIED IN A DESIGNATED FREQUENCY

摘要

A designated burst signal specified in a designated frequency is detected from an all-inclusive signal specified in a number of different frequencies. The frequency of the allinclusive signal is first multiplied by a multiplying factor so as to produce a multiplied output signal. Then a phase-lock loop operation is performed between the multiplied output signal and an oscillated signal produced for performing the phase-lock loop operation and specified in a multiplied frequency of the designated frequency by the multiplying factor. This produces a phase-lock output signal and which is then compared with the multiplied output signal to produce a detected output signal representing whether the designated burst signal is in the all-inclusive signal.