Digital Implementation of Costas Loop with Carrier Recovery

Abstract:- Demodulator circuit is a basic building block of wireless communication. Digital implementation of demodulator is attracting more attention for the significant advantages of digital systems than analog systems. The carrier signal extraction is the main problem in synchronous demodulation in design of demodulator based on Software Defined Radio. When transmitter or receiver in motion, it is difficult for demodulator to generate carrier signal same in frequency and phase as transmitter carrier signal due to Doppler shift and Doppler rate. Here the digital implementation of Costas loop for QPSK demodulation in continuous mode is discussed with carrier recovery using phase locked loop.