A data receiving system comprising an I base-band signal and a Q base-band signal which are used in a quadrature demodulation operation. Zero-crossing points of respective base-band signals are detected and a control signal is generated in response to each zero-crossing point. A phase-shift switching...http://www.google.com/patents/US5293408?utm_source=gb-gplus-sharePatent US5293408 - FSK data receiving system
