Model-Based Compensation of SAR Nonlinearity

In the successive approximation analog-to-digital conversion principle, sample-and-hold (S/H) nonideality, producing an input signal variation that is less than the least significant bit (LSB) during the conversion time, gives rise to intrinsic and significant dynamic nonlinearity. In this paper, a method for compensating such nonlinearity is proposed. Theoretical fundamentals of the method are reported by paying particular attention to the accuracy of the compensation. With this aim, the dynamic phase distortion that is related to the intrinsic dynamic nonlinearity is modeled first. Then, a compensation technique based on the definition of compensated output levels maximizing the signal-to-noise-and-distortion (SINAD) ratio, namely, a particular case of the Max-Lloyd conditions for minimizing distortion in nonuniform quantizers, is applied. Simulation and experimental results show the method effectiveness in compensating the intrinsic dynamic nonlinearity and in incrementing the SINAD ratio in actual working conditions.