Linearized phase lock loop FM-demodulator

Claim 1

A circuit for minimizing the nonlinearity in the zero-axis crossing of a phaselocked loop of an FM-demodulator including: a phase detector which receives an input signal and produces an output signal corresponding to the phase of said input signal and a center frequency; a circuit means for producing a circuit output signal in accordance with said phase detector output signal, said circuit means being adjustable to control the zero crossing linearity of the phase detector by producing a zero voltage level output signal when said input signal is at the center frequency of said phase detector; a voltage controlled oscillator coupled between said circuit means and said phase detector to regulate said phase detector output; and wherein said circuit means includes a filter means coupled to the output of the phase detector; capacitor means coupled between the voltage controlled oscillator and an element with variable capacitance; decoupler means for coupling the output to said element; and an adjustment means connected to the element to vary the voltage at the element and correspondingly allow for a zero voltage output from the phase detector at the center frequency of a signal being demodulated. PG,9