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.
|
 |