12.3.15

You are invited to attend a lecture

By

Moty Roudstein

(M.Sc. student under the supervision of Prof. Amir Boag)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Multilevel Physical Optics Algorithm for

Near-Field Double-Bounce Scattering

Many radar and sonar applications require evaluation of the field scattered from complex objects.  Usually, the scattered field is of interest for various angles of interest at several frequencies within a certain band.  The range of distances to the target is often such that, for the desired frequencies, it is within the target's near field.  At high frequencies, where the physical Optics (PO) approximation is valid, the scattered field can be divided into a series of separate contributions, depending on the number of bounces.  For concave geometries, accurate computation of the scattered field requires, taking into account at least the second order term in the series, namely the "double-bounce" (DB) contribution, i.e., in addition to the "single-bounce" (SB) contribution.  In terms of the computational complexity (CC), this DB contribution is, often, significantly more difficult to compute than the easier SB contribution.  This high CC impedes the calculation of DB contributions, and calls for a faster method.

In this talk, we present a fast algorithm for the evaluation of the DB contributions to the PO scattering integrals, over a range of aspect angles and frequencies.  The work extends the preceding far-field algorithm, to encompass three-dimensional and near-field scenarios.  The algorithm relies on the observation that partial contributions to the backscattered patterns, due to pairs of subsurfaces of a finite size, are essentially band-limited functions of the aspect angles, distance, and frequency.  Multiplying these contributions by appropriate common phase factors allows for their sampling over a coarse grid of source/observation points at rates which are dictated by the subsurfaces' linear dimensions.  Savings are achieved by directly evaluating the partial contributions due to very small subdomains on coarse grids at a very low cost, and then gradually interpolating and aggregating the contributions to obtain the backscattered field due to large subdomains, in a hierarchical fashion.  The presented DB Multi-Level Physical Optics (MLPO) method achieves a significant reduction in the CC.

Thursday, March 12, 2015, at 16:00

Room 011, Kitot building