In this paper, a new technique for characterization of digital-to-analog converters (DAC) used in wideband applications is described. Unlike the standard narrowband approach, this technique employs least square estimation to characterize the DAC from dc to any target frequency. Characterization is performed using a random sequence with certain temporal and probabilistic characteristics suitable for intended operating conditions. The technique provides a linear estimation of the system and decomposes nonlinearity into higher-order harmonics and deterministic periodic noise. The technique can also be used to derive the impulse response of the converter, predict its operating bandwidth, and provide far more insight into its sources of distortion

This paper describes the design of two half-rate clock and data recovery circuits for optical receivers. Targeting the data rate of 10-Gb/s, the first implementation incorporates a ring oscillator and a linear phase detector whereas the second implementation uses a multiphase LC oscillator and a bang-bang phase/frequency detector. Fabricated in 0.18-μm CMOS technology, the power consumption of each of the circuits is less than 100˜mW. The rms jitter of the output clock for the two prototypes is 1˜ps and 0.8˜ps, respectively, while the latter achieves a capture range of more than 14%.