Post-correction of analog-to-digital converter for different input signals

Abstract

A novel post correction method with real-time FPGA implementation is proposed to correct the distortion generated by high-speed Analog to Digital Converters (ADCs). It is achieved by simplifying the dynamic deviation reduction based Volterra series to form an accurate model to effectively compensate both static nonlinearities and memory effects. Both post correction model generation and model extraction modules can be readily implemented in FPGA, which provides great flexibilities in realizing real-time calibration. Experimental results demonstrated that excellent calibration performance can be achieved with very low implementation complexity by employing the proposed method. The fundamental observation, upon which this work is motivated, is that practical analog-to-digital converters are prone to produce errors, i.e., deviations from the ideal operation. The term ‘post correction’ indicates that the correction methods considered in this work are applied after the converter, thus operating on the digital signal provided from the output. One of the constraints for this work is that the internal signals and states of the analog-to-digital converter under consideration are unavailable to us. The goal of the correction is, naturally, to make the corrected output from the converter more true to the ideal output, in some sense; as we will see later on, there are many ways to measure the performance of a converter. Error correction of ADCs has received increasing attention during the last two decades. These methods have in common that the ADC to be corrected is treated as a closed entity, i.e., internal signals and states of the ADC are not available, and the calibration and correction methods must operate outside of the converter. Moreover, the correction is dependent on the output signal x(n) of the ADC to be corrected. That is, the correction is an operation incorporated after the ADC, hence the name post-correction. This paper introduces the present status of analog to digital converter for sine waveform (sine wave). Based on the fundamental principle, the paper then focuses on the different input waveforms such as pulse, triangular type, and square sine for analog to digital converter and compared few ADC parameters like SFDR and SINAD.