Digital FSK demodulator circuit

摘要

An FSK demodulator is disclosed suitable for use in a CMOS IC using switched capacitor circuits. The mark and space filters are each modified to produce sine and cosine outputs. These outputs are rectified separately and the result summed. The summed outputs are passed through low pass filters and applied to a comparator which determines which of the mark and space signals is dominant. The invention substantially reduces the size of the demodulator filter capacitors and improves the demodulation signal to noise ratio.