Implementation of carrier recovery for high-order QAM in real-time multi-domain analysis

摘要

Based on a real-time multi-domain signal analysis SOC architecture for high-order Quadrature Amplitude Modulation (QAM) signals, a VLSI implementation of high-precision non-data-aided carrier recovery (CR) algorithm for high-order QAM analysis and specifications measurement is presented. The proposed CR, which can blindly counteract the large carrier frequency offsets at fast speed in analysis frequency span and realize the jitter-free phase tracking, consists of a blind carrier frequency offset estimator based on Discrete Fourier Transform (DFT) to acquire large carrier frequency offset rapidly, a phase-frequency detector (PFD) to track and compensate the comparatively small frequency error, and a simple decision-directed phase detector (PD) for jitter-free phase tracking. Since the DFT in the spectrum analysis is reused in the CR, the hardware complexity for dual mode is dramatically reduced. Finally, the CR are implemented by FPGA. It takes less than 200 symbols to overcome the large frequency offset of 400kHz, and leaves the dual-mode part a frequency offset about 10kHz, and it takes less than 1000 symbols to converge. When implemented, the total gate is 4125, and the total multiplier is 16.