Benjamin Peterson, Keith Gross, and Ellen Shirvell

Peer Reviewed

Abstract: A summary of ongoing research analyzing the VLF noise environment and various structures of nonlinear Omega receivers is presented. First, the noise amplitude is seen to have a probability density function that can be modeled as Gaussian for small amplitudes and as decreasing proportionally to (amplitude)-2.2 for large amplitudes. This model of probability density function suggests a maximum likelihood nonlinearity that is linear for small amplitudes and of the form f(x) ~ l/x for large amplitudes. Analysis of the behavior of two approximations of this nonlinearity (hole punch and clipper) is presented. Issues addressed include performance relative to a linear receiver as a function of structure, threshold for either nonlinearity, bandwidth prior to nonlinearity, and signal level. The study included both synthesized signals added to actual noise and off-the-air signals. Improvements of 7-14 dB relative to a linear receiver were observed. Finally, it is observed that the presence of a strong local Omega station within the receiver passband results in virtually no improvement for a weaker station, relative to a linear receiver.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 37, Number 3
Pages: 217 - 232
Cite this article: Peterson, Benjamin, Gross, Keith, Shirvell, Ellen, "ANALYSIS OF NONLINEAR OMEGA RECEIVERS", NAVIGATION, Journal of The Institute of Navigation, Vol. 37, No. 3, Fall 1990, pp. 217-232.
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