Front-End ADC Requirements for Uniform Bandpass Sampling in SDR

Changing user scenarios demand wireless connectivity among different standards. As a result, reconfigurability is becoming a key issue in the design of future wireless terminals. In analog front-ends, reconfigurable components are very expensive in terms of design cost and area. Bandpass sampling and digital front-end solutions in general, move the ADC closer to the antenna, avoiding most of the reconfigurable analog hardware. We consider the extreme case of bandpass sampling at RF and analyze the ADC requirements for a multi-standard radio. Two different models, one based on cascade analysis and the other on time-domain simulations, are used with a representative set of emerging wireless standards to derive the ADC requirements: sampling frequency, resolution and clock jitter. This study shows that, with modest RF filtering, RF bandpass sampling will soon become a reality for low power terminals.