An analysis of the LMS adaptive filter used as a spectral line enhancer
Naval Undersea Center, 1975 - Science - 25 pages
The adaptive line enhancer is a new device with unique capabilities. The device has significant applications in the enhancement of narrowband spectral lines in a broadband noise field when there is a poor signal-to-noise ratio at the input and there is insufficient a priori information on which to design appropriate filters. The device automatically filters out the components of the signal which are uncorrelated in time and passes the correlated portions. Since the properties of the device are determined solely by the input signal statistics, the properties of the filter automatically adjust to variations in the input signal statistics to obtain the LMS approximation to a Weiner-Hopf filter. The device will thus track slowly varying spectral lines in broadband noise. This paper derives the properties of an N-weight adaptive line enhancer for a single stable input spectral line in both an arbitrary and a white noise background. The fundamental properties of the adaptive line enhancer are discussed in terms of these solutions. (Author).
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adaptive line enhancer autocorrelation matrix bandwidth broadband noise reduction cjQj complex spectral line computer simulations crosscorrelation vector delay line derived design appropriate filters electronic filter gain filter output frequency input and output input signal statistics input signal-to-noise ratio input spectral line input waveform consists line in white lines in broadband LMS ADAPTIVE FILTER LMS weight vector magnetic tape magnitude matched filter mean square error N-weight filter narrowband filter narrowband spectral National Technical Information NAVAL UNDERSEA CENTER noise component noise power NTIS collection number of weights output power parallel channels passband priori information properties real input signal reduced to wLms reports sampled waveform sampling rate shown signal and noise signal at 1000 signal correlation matrix signal-to-noise enhancement single complex spectral single spectral line spectral components SPECTRAL LINE ENHANCER stable spectral lines summing junction Technical Information Service time-delayed signal uncorrelated vector product white noise input Widrow Wiener-Hopf