Spectral-Line Timing Recovery in Digital Data-Communication Systems

Abstract—In many of the digital communication systems where a form of passband modulation scheme is used, carrierless amplitude and phase modulation (CAP) or quadrature and amplitude modulation for example, the signal waveform does not contain a baud-rate spectral line. This paper describes analog and all-digital implementations of timing recovery using the nonlinear spectral-line method. The analog implementation of the timing-recovery integrated circuit was fabricated in 0.9- m CMOS process and verified to meet all the requirements for a system utilizing the CAP modulation scheme, and initial results of the all-digital implementation confirm an even better performance that is process independent. The 51.84-MHz recovered clock allows the receiver to achieve better than a IH IH bit-error rate (BER). Index Terms—Carrierless, carrierless amplitude and phase modulation (CAP), CMOS, digital communication, nonlinear spectral line, quadrature and amplitude modulation (QAM), timing recovery. I