Sensitivity Analysis of Continuous-Time $\Delta \Sigma$ ADCs to Out-of-Band Blockers in Future SAW-Less Multi-Standard Wireless Receivers

The increasing demand for integrating multiple wireless services in one multi-standard handset, exemplified by the software-defined radio (SDR) model, calls for digitizing wireless receivers in a quest for flexibility. Radio-frequency (RF) front-end and analog baseband filters need to be exchanged for digital processing at the expense of a highly challenging analog-to-digital converter (ADC) specifications. In this paper, the sensitivities of continuous-time (CT) delta-sigma (ΔΣ) ADCs, which are candidate architectures for multi-standard receivers and SDRs, to out-of-band (OOB) blockers at the ADC input are investigated. This analysis addresses the problems and performance limitations that can result from large OOB blockers appearing at the input of CT ΔΣ modulators in a digitized multi-standard receiver. Analysis and discussions given in different sections of the paper are verified by CT system-level simulations.