Towards an Interference-Mitigation Transmitted-Reference Ultra-Wideband ReceiverKen Townsend (supervisor: Dr. Jim Haslett)
MSc Thesis, University of Calgary, Department of Electrical and Computer Engineering, August 2007
Designers of Ultra-Wideband communication systems must consider the impact of narrowband interference on link performance. In general, degradation will be worse in receivers that use impulse-radio modulation schemes, given their inability to avoid interference within the band. In this thesis,k a fully integrated interference-mitigating transmitted-reference Ultra-Wideband autocorrelation receiver archit3ecture is proposed. A link budget is established to define subsystem requirements, and a number of circuits are then described that make future realization feasible.
The first stage of the receiver's front-end uses a unique low noise amplifier to achieve a wideband input match. The amplifier is followed by an integrated differential bridged-T notch filter for interference cancellation. Post-processed solenoids are investigated as an alternative to traditional on-chip spiral inductors, and incorporated into the front-end in 0.18μ CMOS.
A wideband power detector is developed to tune the notch filter, again in 0.18μ CMOS. The detection technique uses devices operating in the triode regime to generate an average current proportional to input power; this current is converted to voltage and amplified using a piecewise-linear logarithmic approximation. Optimization of the devices is discussed, as is a method of gain control for compensation against temperature and process variation.
Finally, a high-speed time-based analog-to-digital converter based on voltage-to-time and time-to-digital conversion is presented. The time-to-digital converter relies on parallel tunable delay lines to maximize timing flexibility. This circuit enables the high-speed quantization and delay of the UWB signal for autocorrelation. A combination of measurement and simulation are used to evaluate effectiveness in 90nm CMOS.
CONTACTS: Ken Townsend, Jim Haslett
SUBJECTS: RF Circuits and Systems
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