Date of Award

Spring 1992

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Mulligan, Michael G.

Second Advisor

Heinen, James

Abstract

This thesis presents a new class of pseudorandom binary sequence generators for Direct Sequence Spread Spectrum (DSSS) communications. These generators, called Nested Linearly Combined (NLC), produce sequences by linearly combining the output from an echelon of Linear Feedback Shift Registers (LFSR). Clocking for upper registers is derived from the period of the register directly below. This results in an overall period that is equal to the product of the periods for the individual LFSR's. The sequences produced by this new class of generators have statistical properties that can be incorporated into a system design. The autocorrelation function of an NLC sequence exhibits small peaks at time lags corresponding to periods of the different levels. An acquisition system is presented that uses this property to acquire sequence phase in less than one period. The acquisition system is analyzed using a Markovian state transition fl.ow graph and the results are corroborated by computer simulation.

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