Spread spectrum signal characteristic estimation using exponential averaging and an ad-hoc chip rate estimator

摘要

This dissertation investigates two methods of spread spectrum (SS) signal characteristic estimation for the two principle types of SS systems, frequency-hopped (FH) and direct sequence SS. The exponential averaging detector is used to detect and estimate the hopped frequencies for a SS-FH signal in the presence of interference signals as well as additive-white-Gaussian-noise (AWGN). The detection method provides an estimate of the AWGN plus interference spectrum using exponential averaging and then generates an estimate of the desired signal spectrum by combining the estimated AWGN plus interference spectrum with the composite (desired signal plus interference plus AWGN) spectrum. Finally, this dissertation evaluates the detector's performance as a function of the exponential coeeficient, the combining method, the probability of false alarm, signal-to-AWGN ratio, and signal-to-interference ratio. The second method of SS signal characteristic estimation uses a signal ad-hoc chip rate estimator (ACRE). The ACRE is used to estimate the chip rate of a half-sine pulse shaped SS direct-sequence signal. The Acre is explained in relation to its similarities and contrasts to the chip rate detector. The components and performance of the ACRE are presented for standard-ACRE. ACRE with additional filtering, and ACRE with incrementing. The additional filtering results in a reduced chip rate search range but yields improved estimation performance and incrementing has the potential for parallel processing, resulting in dramatically decreased computational time, without loss of performance.