Methodology and Measurement Setup for Analog-to-Digital Converter Postcompensation

We present a methodology for nonlinearity compensation amenable to a wide variety of analog-to-digital converters (ADCs). To that purpose, a postcompensation scheme for a commercial ADC is presented and two compensator models are considered: the memory polynomial (MP) and the modified generalized MP. Since the proposed method does not use any information about the compensated architecture, it can be applied to different ADC designs. Furthermore, we address the measurement and characterization setup of the device under test by making a study of the quality of the signals involved to verify the improvement obtained. The issue of the training sequences required by the proposed compensation method is also addressed in detail. Despite the common use of a single training signal, we propose to use several sinusoids in the bandwidth of interest. With this, it is possible to show that the generalization properties of the estimated postcompensator are greatly enhanced compared with the case of a single sinusoid training sequence. As verified by the measurements, considerable gain in accuracy can be obtained using the proposed methodology. In particular, a 10-dB increment in spurious free dynamic range is obtained using the proposed postcompensators over the complete Nyquist frequency band.