On the implications of analog-to-digital conversion on variable-rate bandpass sampling GNSS receivers

As radionavigation signals will be in multiple bands within the next decade, a software-defined wideband receiver will enable painless tuning into the bands of interest to comply with the required modulation standard. Nevertheless, such a receiver puts extreme requirements on the Analog-to-Digital Converter (ADC) in terms of sampling rate, dynamic range, and power dissipation such that a feasibly conceivable solution will not be available in the near future. An alternative solution is to utilize a variable-rate BandPass Sampling (BPS) receiver to relax the requirements of the ADC whilst eliminating the need for analog mixers and image-rejection filters. This paper first introduces the variable-rate BPS GNSS receiver and then gives an analysis of SNR degradation due to various noise sources and presents design considerations for the proposed receiver. A comparative study is carried out for Flash ADC and Continuous-Time (CT) Delta-Sigma (Δ∑) ADC as well as providing a signal chain noise analysis for both cases.