A QPSK modulation scheme uses a data spreading mechanism to rob a relatively limited portion of available transmitter power, and inject into the QPSK waveform a prescribed amount of carrier signal power, through which detection and non-regenerative extraction of the carrier at the receiver may be achieved...http://www.google.com.hk/patents/US6606357?utm_source=gb-gplus-share專利 US6606357 - Carrier injecting waveform-based modulation scheme for reducing satellite transponder power requirements and earth terminal antenna size
