CMOS implementation of nonlinear spectral-line timing recovery in digital data-communication systems

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-μm 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 10^-10 bit-error rate (BER).