用NE564做1.8MHz频移键控译码器

The NE564 PLL is particularly attractive for FSK demodulation since it contains an internal voltage comparator and VCO which have TTL compatible inputs and outputs, and it can operate from a single 5V power supply. Demodulated DC voltages associated with the mark and space frequencies are recovered with a single external capacitor in a DC retriever without utilizing extensive filtering networks. An internal comparator, acting as a Schmitt trigger with an

adjustable hysteresis, shapes the demodulated voltages into compatible TTL output levels. The high frequency design of the 564 enables it to demodulate FSK at high data rates in excess of 1.0M baud.