Cope, Michael K. Design, Simulation, and Implementation of a Digital Quadrature Demodulator for a Stepped Frequency Radar. MSc Dissertation. Department of Electrical Engineering, University of Cape Town, 2003.
This thesis describes the model used to investigate the effects of Phase Noise and Quantisation noise on the IF quadrature detector of a SFCW radar.
The scope of this thesis is the design and implementation of a digital quadrature demodulator for a stepped frequency ground penetrating radar. This dissertation presents a theoretical model of the demodulator, simulations characterising the demodulator performance, as well as the design, construction and measurement of the prototype demodulator.
The demodulator estimates the amplitude and phase of the intermediate frequency signal of a time-interleaved dual-channel heterodyne radar receiver. A demodulator model is developed from a survey of the relevant literature, paying particular attention to errors introduced in sampling. Simulations predict the demodulation performance in the radar system, suggesting coherent integration improves acuracy by reducing the effect of random sampling errors. The design of the prototype and characterisation of its performance are briefly reported.
Measurements confirmed that coherent integration increased the demodulator accuracy. Timing jitter was found to be the most significant cause of error, due to phase noise in the IF signal. The simulations predicted that the demodulator would not meet the specified performance; measurement determined the prototype’s accuracy to be within specification, although the test signals were of higher quality than the expected radar IF signal.