Feature extraction for classification of signals propagating in channels with dispersion and dissipation

In active sonar or radar, if the channel is spatially- and/or temporally-varying, then the target echo can change with propagation, such that echoes from identical targets may not be identified as such at the receiver. Two common propagation effects that induce changes in the signal are dispersion and dissipation (or damping), which give rise to frequency-dependent velocity of propagation and frequency-dependent attenuation, respectively. We have previously developed a feature extraction process for target echoes in dispersive channels, to obtain moment-like features that are invariant to dispersion, per mode. Accordingly, even though the target echo can change with propagation in a dispersive channel, the "dispersion-invariant moment" features do not. However, these moment features are affected by damping. In this paper, we consider the case of a channel with dispersion and damping, and derive features that are invariant to both phenomena, for any dispersion relation and exponential or power-law damping. Results are presented from classification simulations to demonstrate the utility of these features.