Patent ID: 6590377
Filing Date: 2003-07-08
Classification: G01R

Abstract:
A frequency detection circuit for measuring in the presence of noise and interfering frequencies the frequency components contained in a tone burst comprising:a) a phase lock loop circuit with an oscillator having a free-running frequency and having input, control, and output stages, said input stage receiving said tone burst, said control stage being responsive to control means to control said free-running frequency, and said output stage providing an output signal having a frequency corresponding to said frequency of said tone burst; and b) a microprocesor having at least one stored predetermined quantity representative of a predetermined frequency serving as a selectable standard for measuring said frequency components contained in said tone burst and having an output stage and an input stage, said input stage connected to said output stage of said phase lock loop circuit, said output stage connected to said control stage of said phase lock loop circuit, said microprocessor having means for measuring said frequency of said output signal of said phase control loop circuit and generating an output signal when said stored predetermined frequency equals said frequency of said output signal of phase loop circuit.