Abstract:

The carrier PLL is usually used for the signal synchronization between local generated carrier signal and received carrier signal.Costas loop is the commonly used non-coherent carrier PLL with well phase discrimination characteristic. This paper based on the principle of Costas loop used single channel carrier PLL designs a improved Costas loop which can be used by the carrier PLL for double channel balanced QPSK+DSSS and deduces the error signal of phase discrimination signal，finally，the improved Costas loop is simulated principally，as result，it may realize stable tracking of carrier phase for double channel QPSK+DSSS.

Key words: Costas loop, QPSK demodulation, carrier PLL, DSSS