Date of Award

Spring 1985

Document Type

Dissertation

Degree Name

Doctor of Engineering Science in Electrical Engineering

Department

Electrical Engineering

First Advisor

Sol Rosenstark

Second Advisor

Jacob Klapper

Third Advisor

Joseph Frank

Fourth Advisor

John Tavantzis

Abstract

By comparison to conventional communication systems, spread-spectrum systems are known to be less affected by interference because of their large dimensionality in signal space. Nevertheless, significant performance degradation is experienced when large interference exists in a few or even one signal coordinates. In this case, interference reduction techniques are also known to provide additional processing gain. A novel class of pseudonoise (PN) invariant algorithms is derived to reduce the impact of interference and restore much of the structure of PN signals received in the presence of interference and noise. A PN signal received by a pre-detection signal process (PDSP) implementing a PN invariant algorithm remains unchanged at the output. When an interference waveform is added to the PN signal, most of the DC bias as well as other smooth components of the interference may be significantly reduced at the output of the same PDSP. If n is the longest run in the PN sequence of maximal length N, and Ro is the chip rate, it is shown that the algorithms work well when the interference is sinusoidal with a frequency deviation from the carrier up to Ro/N. At such a low frequency deviation, the processing gain is observed to be relatively high and independent of the phase deviation. As the frequency deviation Increases to nRo/N, the performance of the spread-spectrum system decreases to the level that would have been obtained in the absence of the PDSP.

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