Smear signature morphology of surface targets with arbitrary motion in spotlight synthetic aperture radar imagery

Abstract

This study develops a methodology for analytically predicting the detailed smear signature morphology of surface targets with arbitrary motion in spotlight synthetic aperture radar (SAR) imagery. The radar sensor is assumed to move with constant speed and heading on a level flight path with broadside imaging geometry. Cases of uniform target motion exhibit morphology of simply curved smear shapes, as has been reported previously. However, the present analysis shows that nonuniform target motion can cause complicated smear shapes in spotlight SAR imagery. Specifically, the method of stationary phase is applied to local subaperture SAR images to yield analytic non-parametric expressions for the morphology of smear signatures within spotlight SAR imagery for surface targets with arbitrary motion trajectories. This predictive capability offers the potential of extracting some characteristics of true target motion based upon the induced SAR smear signatures alone.

Insights into the complicated SAR signature shapes induced by braking targets

“…29 In particular, some investigations 36,37 consider the use a non-zero squint angle in order to examine the effects in which the radar mainbeam is not constrained to point only in the broadside direction. Furthermore, similar methods 61 have been applied for bistatic geometries in order to examine the smears induced by targets which are moving with piece-wise constant velocity segments.…”

“…29,37 uses the methods of a power series expansion applied to sub-aperture images in order to derive general expressions for the central contour of the smear signature for a surface target moving with an arbitrary motion profile. The present investigation examines the case of a surface target with decreasing speed during the SAR collection interval in more detail.…”

“…The use of power series expansions confounds the investigation of complicated target motions, since the number of terms in the resulting expansions becomes quite cumbersome. 16,17,25 These challenges have led to the application of subaperturebased techniques 29 for these problems. In addition, prior studies 30-32 apply analytic power series expansions to subaperture images in order to examine the undesired multipath effects in SAR imagery.…”

“…The challenges of the power series expansion approach led to the development of subaperture-based techniques 29,[33][34][35][36][37] for understanding moving target signatures. Subaperture-based analyses have been performed by various researchers [38][39][40][41][42][43] investigating SAR concepts.…”

Effects of speed difference on accelerating target imagery signatures for broadside SAR

“…A recent analysis [8] also applies subaperture methods to analyze spotlight SAR image signatures for ground-plane targets moving with arbitrary motion. Refs.…”