关键词: 自适应均衡器, 载波同步, 均方误差, 正交幅度调制

Abstract: In view of the characteristics of cable channel, a joint design of adaptive equalizer and carrier recovery loop for high order QAM signals was proposed, which was suitable for ITU-T J.83 standard. The equalizer initially operated in Constant Modulus Algorithm (CMA) mode to compensate the channel distortion. When the eye diagram was opened, the equalizer switched to Least Mean Square (LMS) mode to decrease the Mean Square Error (MSE). For high order QAM signals, the carrier recovery 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. The simulation studies show the good performances of this design. The whole design was synthesized under Altera Stratix Ⅱ EP2S130F1020C5 FPGA. Highest clock frequency after being routed reached as high as 90.47MHz.

Key words: adaptive equalizer, carrier synchronization, Mean Square Error (MSE), Quadrature Amplitude Modulation (QAM)