This paper explores passive switched capacitor
based RF receiver front ends for spectrum sensing. Wideband
spectrum sensors remain the most challenging block in the software
defined radio hardware design. The use of passive switched
capacitors provides a very low power signal conditioning front end
that enables parallel digitization and software control and
cognitive capabilities in the digital domain. In this paper, existing
architectures are reviewed followed by a discussion of high speed
passive switched capacitor designs. A passive analog FFT front end
design is presented as an example analog conditioning circuit.
Design methodology, modeling, and optimization techniques are
outlined. Measurements are presented demonstrating a 5βGHz
broadband front end that consumes only 4βmW power
