Analog–digital conversion signal-to-noise ratio analysis for synthetic aperture interferometric radiometer

Abstract

A nontrivial analog–digital conversion (ADC) signal-to-noise ratio (SNR) analysis for synthetic aperture interferometric radiometers for microwave remote sensing is presented. Correlation uncertainty is a key issue in the digital processing of radiometric signals. The ADC digitizes the analog intermediate frequency signal to perform digital correlations, hence the ADC noise is critical for radiometric performance, but this effect has lacked sufficient analysis. First, the ADC SNR requirement is drawn, and ADC SNR degradation is attributed to input noise, quantization noise, and sampling jitter. Second, it is proved that the input and the quantization noise have negligible effects on visibility uncertainty. Third, it is shown that the sampling jitter should be stringently controlled by Gaussian noise digitization SNR requirement. The sampling clock jitter is the dominant contributor in jitter caused SNR, and is evaluated by the long-term statistical time interval error jitter. Finally, the sampling jitter, the realized ADC SNR ratio and visibility uncertainties are tested on BHU-2D-U radiometer to verify the demonstrations. The analysis results can be used as a guideline in the digital correlation design of polarimetric or synthetic aperture radiometric systems.