Showing papers on "Quadrature mirror filter published in 1977"

Angle-modulation detector having push-pull input applied through high-pass filters

Abstract: A circuit adapted to detect an angle-modulated signal including a pair of terminals to which the angle-modulated signal is supplied in push-pull relation and a high-pass filter circuit coupled to the pair of terminals for transmitting those frequencies of the angle-modulated signal which exceed a cut-off frequency. A differential amplifier has a pair of inputs coupled to the high-pass filter circuit to receive the filtered angle-modulated signal as a reference signal and a quadrature generator is coupled to the high-pass filter circuit and is responsive to the filtered reference signal for generating a quadrature signal whose phase varies with respect to the reference signal as a function of the change in frequency of the reference signal. A multiplier is coupled to the differential amplifier outputs and includes an input for receiving the quadrature signal so as to be switched in response to these respective signals for producing an output signal which is a function of the phase difference between the reference and quadrature signals.