Design of carrier recovery for QAM/VSB dual mode

In this paper, an architecture and hardware implementation of the carrier recovery (CR) used in dual mode (QAM and VSB) transceiver for digital CATV is proposed. The proposed CR uses decision-directed approach with steep gradient algorithm, which can be used in both QAM and VSB signal. Thus, the hardware complexity for dual mode is dramatically reduced, while the performance is almost the same. To increase the acquisition range of CR, a frequency locked loop (FLL) is used in VSB mode while a derotator/rotator pair is adopted in QAM mode. As a result, the CR can reach ±100 KHz acquisition range. Finally, the CR is implemented by TSMC 0.35um 1P4M process. The total gate is 20820 and the maximum symbol rate is 21.52 M Baud.