Implementation and Design of Carrier Recovery Loop for High Order QAM Signals

Based on coordinate rotation digital computer (CORDIC) algorithm and phase frequency detector (PFD), a new design of digital carrier recovery loop for high order QAM signals was presented. The loop initially operated in polarity decision algorithm (PDA) under fast and slow modes which were set in loop filter (LPF) to capture the frequency offset. When the frequency offset was captured, the loop switched to decision direct algorithm (DDA) to decrease the phase jitter. We proposed digital direct frequency synthesizer (DDFS) under CORDIC algorithm, with more accuracy and more feasibility on very large scale integrated circuits (VLSI) implementation of carrier recovery circuit than conventional look-up table. Simulations showed the good performance of this design. By FPGA implementation, the efficiency was proved.