Time-Variant Characterization and Compensation of Wideband Circuits

Many wideband circuits use interleaving to extend bandwidth leaving them with a cyclically time-variant output. This paper describes a technique for characterization of these types of circuits based on least-squares estimation of the time-varying response of circuits. Applying the methodology to a 90-nm, 12-GS/s 8-bit digitally-equalized DAC, shows significant timing varying behavior. Furthermore, using the data obtained from characterization to construct linear time-variant compensation improves the DAC signal-to-distortion ratio by at least 6 dB.