Thesis Abstracts 2002
Research and Graduate Studies Electrical and Computer Engineering
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Novel Design Approach and Architectures for Sinusoid Output Direct Digital Frequency Synthesis
By: Lieutenant-Commander, Pierre Langlois
Supervisor: Dr. Dhamin Al-Khalili
Abstract
Direct Digital Frequency Synthesis (DDFS) makes it possible to generate single phase or quadrature sinusoids over bandwidths measured in hundreds of megahertz, with sub-hertz frequency resolution, unparalleled frequency hopping rates, and phase continuity on hopping. These characteristics make DDF Synthesizers ideal in a wide array of applications, including spread-spectrum communications, radar, instrumentation and broadcasting. Design challenges include maintaining high spectral purity, high clock rates and low power consumption.
This thesis presents a novel approach to the design of sinusoid output DDF Synthesizers with Phase-to-Sine Amplitude Converters based on linear interpolation. For such synthesizers, the first quadrant of the sine function is approximated with piecewise-continuous linear segments. Simple control circuitry reconstructs a full sine wave by symmetry.
Basic principles of DDFS are presented, and a comprehensive review of existing work is made. A spectral analysis of the linear interpolation of the sine function is given, from which a design procedure is derived for the number of segments required and the value of system parameters to achieve a desired spectral purity. New hardware-optimized single phase and quadrature DDFS architectures are presented, and their validity is supported by several designs implemented with three different technologies. The new design approach and architectures are compared with existing work and are shown to produce designs with significantly reduced complexity and power consumption for equal performance.
