Accession Number : ADA317497

Title :   Systematic Splitting of Wavefields into Unidirectional Modes: Long-Range Asymptotic Methods for Weakly Uniform Media,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC ANALYTICAL ACOUSTICS SECTION

Personal Author(s) : Gragg, Robert F.

PDF Url : ADA317497

Report Date : 08 AUG 1996

Pagination or Media Count : 45

Abstract : A series of pseudo-unitary transforms is devised and applied to the Helmholtz equation for a weakly nonuniform one-dimensional medium, decoupling the wave field in a consistent order-by-order way into counter-propagating modes. The result is a generalized form of d'Alembert decomposition, providing an asymptotic solution without backscatter at arbitrary order. Low-order contributions correspond to the standard WKB approximation. Higher orders provide additional terms of potential importance in applications involving propagation over long ranges, e.g., long time-of-flight measurement and very-long-baseline interferometry. Evidence is presented that this decoupling scheme is equivalent to high-order Born approximations.

Descriptors :   *WAVE PROPAGATION, *WAVE EQUATIONS, MEASUREMENT, BACKSCATTERING, BEAM SPLITTING, INTERFEROMETRY, ASYMPTOTIC SERIES, DECOUPLING, DECOMPOSITION, UNIDIRECTIONAL, HELMHOLTZ EQUATIONS.

Subject Categories : Numerical Mathematics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE