This thesis discusses the limitations of wideband software defined radios (SDR).
Spectrum sensing is identified as an important aspect required of SDR based cognitive
radios. Several architectures and implementations are reviewed. An RF sampler followed
by analog signal processing is identified as a critical block enabling low-power
Passive switched-capacitor charge-domain processing is introduced. Its implementation
simplicity and lack of active power consumption are enticing. The effect of kT/C
noise is analyzed in detail. Linear and nonlinear computation errors are modeled, and
circuit techniques for their reduction are developed. Simulations are used to optimize
power and computational dynamic range.
For spectrum sensing, the design of CRAFT (Charge Re-use Analog Fourier Transform):
an RF front-end channelizer for wideband software defined radios based on a
16-point analog-domain FFT is described. The design relies on charge re-use to process
a 5GS/s input with an average output SNDR of 47dB, and consumes only 12.2pJ/FFT
conversion (3.8mW). These numbers represent orders of magnitude improvement on the
work reported previously in literature. The thesis also discusses the system-level modeling
and mitigation of circuit non-idealities in CRAFT. These design principles enable
this implementation to achieve a large dynamic range even at high speeds. Additionally,
these techniques can be easily extended to improve the performance of other passive
University of Minnesota Ph.D. dissertation. January 2013. Major: Electrical Engineering. Advisor: Prof. Ramesh Harjani. 1 computer file (PDF); xi, 174 pages, appendices A-C.
Passive switched-capacitor based filter design, optimization, and calibration for sensing applications.
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