Circuit arrangement for demodulating a frequency-modulated signal

摘要

To demodulate a frequency-modulated signal in digital representation, the successive digital values are supplied to a multiplier directly via one input and via a delay section via the other input. The product supplied by the multiplier contains a signal component with twice the frequency of the frequency-modulated signal supplied, which is filtered out by a low-pass filter. Furthermore, a signal component exists which contains the instantaneous frequency of the frequency-modulated signal. An essentially linear demodulation is obtained if the delay time of the delay section 4 corresponds to one quarter of the mean period of the input signal. The low-pass filter is suitably formed from a shift register, a number of multipliers which can be implemented by means of adders, and a summing circuit, as digital transversal filter. <IMAGE>