An Implementation of All-Digital Coherent Demodulator Based on FPGA

Coherent demodulation has excellent noise immunity and error performance, widely used in the all--digital receiver. Carrier synchronization and bit synchronization are the key technologies directly affecting the demodulation performance. Take QPSK signal for example, this paper uses evolutionary costas loop to achieve carrier synchronization, and PLL structure based on digital interpolation and Gardner algorithm to recover timing clock. From the perspective of project application, some key points of hardware implementation are discussed in detail. The feasibility and correctness of this design are verified on a low--cost Field Programmable Gate Array (FPGA) chip, the demodulator has good anti-- noise, high-- speed and real-- time performance, with great reference value of engineering.