Patent ID: 6188733
Filing Date: 2001-02-13
Classification: H04L

Abstract:
A center frequency detecting circuit for an FSK signal receiver for detecting a DC center level of a base-band signal wherein a base-band signal obtained through demodulation of a received FSK signal is applied to a first positive input of an addition/subtraction circuit as well as to a waveform shaping circuit for shaping it into a rectangular wave which constitutes a demodulated output signal, said demodulated output signal being input to a negative input of said addition/subtraction circuit after it was made equal to said base-band signal in amplitude, and said addition/subtraction circuit providing an output which is adapted to be smoothed to obtain a detected error, said center frequency detecting circuit comprising:circuit means for correcting the above error detecting operation, said circuit means configured to receive said base-band signal and said demodulated output signal and configured to supply a correcting signal to a second positive input of said addition/subtraction circuit.