Wide Band RF ADC Conversion Artefacts and their Impact on Radio Astronomy

Abstract

Current trends in state-of-the-art RF Analogue to Digital Converters (ADCs) indicate that their performance is approaching theoretical bounds imposed by the jitter noise of the supplied/distributed sample clock [1], [2]. In the first part of this paper, we show that ADC jitter noise, in the presence of strong, band-limited input signals, impacts the noise-floor performance of high-resolution ADCs which has a particularly harmful effect on pulsar radio astronomy. Furthermore, many of the current wide bandwidth RF ADCs typically rely on precise time-interleaving of several lower-rate ADCs to achieve high output resolution at the full Nyquist rate (see e.g. [3], [4]). In the second part of this paper, we present a new adaptive technique to mitigate the residual effects of time-interleaving artefacts from high-performance ADCs caused when strong, band-limited RFI is present at the converter input.