FM demodulator apparatus and method includes an amplitude locked loop and a delay-line quadrature detector without the use of a limited amplifier

摘要

The present invention relates to an FM demodulator incorporating a delay-line quadrature detector without the use of a limiter amplifier. An Amplitude Locked Loop circuit provides a carrier signal with no amplitude variation prior to performing a conversion from frequency modulation to phase modulation. A delay-line performs this conversion using a standard IF ceramic filter with a precise delay of 90 degrees to the un-modulated carrier frequency. The original non-delayed carrier is multiplied with the delayed carrier using a four quadrant linear multiplier to generate a demodulated audio output.