Enhancement of Frequency Hopped Signals by Convergence Bandwidth Discrimination

This paper presents a technique for enhancing a wideband signal of narrow instantaneous bandwidth, such as a frequency hopped signal, from wideband and narrowband interference. The central concept is that statistical estimation inherently involves a time average, with an accompanying convergence time. Adjusting the convergence time constant of this estimation process can make the signal of interest (SOI) appear to the estimating device as either narrowband or wideband. A device such as an adaptive line enhancer (ALE) that separates wideband and narrowband waveforms can use this property to distinguish the SOI from interference. Simulation examples are given wherein two ALE's are used in tandem to separate frequency hopped signals from narrowband interference and wideband noise. The result is a relatively clean approximation to the signal that is more easily detected or characterized by an intercept receiver. A second application of this same concept uses a single ALE to separate two frequency hopped signals with very different dwell times.