Design tradeoffs in N-path GmC integrators for direct delta-sigma receivers

This paper analyzes a tradeoff between noise figure, blocker filtering, and noise shaping that is inherent in the recently introduced direct delta-sigma receiver approach. It originates in the competing requirements imposed by the front-end low noise amplifier operating as a transconductor in an N-path G_mC integrator and as a voltage pre-amplifier in a closed-loop radio-frequency front-end. A generic receiver model for evaluating the tradeoff is presented and verified through simulation. We then propose a design method for managing the tradeoff in light of receiver target specifications.