Some Matched Filter Configurations for Infrared Systems

An analysis of the output of three alternative matched filter configurations in an infrared scanning system model is presented. The sensor is corrupted by thermal noise, generation-recombination noise, photon noise, and modulation noise, the latter providing an extreme discoloration in the signal passband. Expressions for the signal voltage density spectrum, signal pulse shape, noise power spectrum, and average noise power at the matched filter output are derived where the integral evaluations attendant to these derivations do not appear elsewhere in the literature. The paper also provides graphical displays of the signal-to-noise power ratio at the filter output versus various system parameters, noise power spectrum out of the matched filter versus ?, and the signal pulse shape out of the filter versus time. Also included are discussions of practically realizable approximations to the matched filters and curve fitting techniques for the signal pulse shape function.     

Some Aspects of Swerling Models for Fluctuating Radar Cross Section

The structure of Swerling's 1957 model for fluctuating radar cross section and signal amplitude is examined prinwrily in terms of mixture representations. The authors also show the relationship of Nakagami's m distrubution to Swerling's amplitude distribution, and Nakagami's q distribution (Hoyt vector density) is reduced to the Swerling distribution. Nonuniform phase distributions associated with Swerling's functions are also derived. Results are given when Swerling's amplitude density is used as a prior distribution with Bennett's (Rice's) distribution for the amplitude of a sine wave plus narrowband Gaussian noise.     

Probability Densities and Characteristic Functions for Fluctuating Targets

Probability density functions and characteristic functions for the projected area of a tumbling target object are derived together with the densities and characteristic functions for the corresponding signal-plus-noise voltage output of an infrared sensor. Several cases are considered in which the signal pulse arrival time is either known or unknown, a matched filter or a suboptimum filter is used; the signal pulse shape is either Gaussian or is unspecified; and the target orientation angles are either uniformly or nonuniformly distributed.