Abstract: 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.

Abstract: There is described a method and apparatus for separating two independently modulated co-channel interfering fm carriers. The method involves generating a numerator signal being a function of generating a numerator function and a denominator function, the numerator and denominator functions being themselves functions of the ratio of the interfering carrier to the wanted carrier and of the instantaneous difference between the frequency of the wanted carrier and the interfering carrier, and performing a division process between said denominator function and said numerator function to generate a quotient function and using said quotient function to condition an output circuit.