Demodulator for F.M. data transmission system - uses switching circuit demodulator based upon gated counter to demodulate signals

摘要

The FM signal demodulation uses transformation into rectangular pulses whose period signals a characteristic frequency. A rectangular comparison signal is derived by an oscillator and a counter. From the rectangular pulses and the comparison signal is obtained a measuring signal, characterising both binary values of the demodulated signal. The demodulated signal is then derived using a low pass and a threshold value stage the duration of the comparison signal is smaller, by a specified value, than the n multiple of the period of the narrow rectangular pulses, n being an integral. The leading and trailing edges of the measuring signal pulses coincide with the individual oscillation pulses.