Implementation of QPSK – demodulator

A coherent QPSK receiver requires accurate carrier recovery using a 4th power process, to restore the 90o phase states to modulo 2p.

In addition an accurate symbol timing recovery circuit is needed for sampling the demodulated filtered data stream. It is possible to use the same methods of symbol timing recovery as proposed for baseband or binary modulation formats.

Data at the output of the comparators is reconstructed into a single data stream using a parallel to serial converter.