High stability wireless microphone circuit

Circuit working principle: After VT1 amplifies the input audio signal , the output
audio signal is added to the varactor diode VD. Since the varactor diode is a voltage-controlled
component, its equivalent capacitance value will change with the change of the input signal voltage, so that
the center frequency of the oscillation of the carrier oscillator composed of VT: and its peripheral components will change accordingly,
forming FM signal.