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[资源] Fundamentals of the Physical Theory of Diffraction 2007

Preface

The physical theory of diffraction (PTD) is a high-frequency asymptotic technique
for the investigation of antennas and scattering problems. This monograph presents
the first complete and comprehensive description of the modern PTD based on the
concept of elementary edge waves (EEWs). Its subject is the diffraction of acoustic
andelectromagneticwavesbyperfectlyreflectingobjectslocatedinahomogeneous
losslessmedium.
The basic idea of PTD is that:The diffracted field is considered as the radiation
generated by the scattering sources (currents) induced on the objects. The so-called
uniform and nonuniform scattering sources are introduced in PTD. Uniform sources
are defined as sources induced on the infinite plane tangent to the object at a source
point.Nonuniformsourcesarecausedbyanydeviationofthescatteringsurfacefrom
thetangentplane.Forlarge convex objects with sharp edges, the basic contributions
to the scattered field are produced by the uniform sources and by those nonuniform
sourcesthatconcentratenearedges(oftencalledfringesources).
Theintegrationofuniformsourcesleadstothephysicaloptics(PO)approxima-
tionforthescatteredfield.ThePTDisthenaturalextensionofthePOapproximation,
taking into accounttheadditional field createdbythenonuniform/fringe sources.
Thisbookprovideshigh-frequencyasymptoticsforfringescatteringsourcesand
for the scattered field in the far zone. Scattering characteristics are calculated for
a variety of objects, such as strips, polygonal cylinders, cones, bodies of revolution
withnonzeroGaussiancurvature(includingparaboloidsandsphericalsegments),and
finitecircular cylinderswithflatbases.
Thetitleofthebookunderlinesthefactthatagreatdealofattentionistobegiven
to scattering physics. The derived analytic expressions clearly explain the physical
structureofthescatteredfieldanddescribe,indetail,allofthereflectedanddiffracted
rays and beams, as well as the fields in the vicinity of caustics and foci.Also, a new
fundamentalcomponentofthefield,theso-calledshadowradiation,isintroduced.It
isshownthatthiscomponentcontainshalf ofthetotalscatteredpower.Thephysical
manifestations of the shadow radiation are the well-known phenomena of Fresnel
diffraction andforwardscattering.
Plotted numeric results supplement the theory and provide visualizations of the
individualcontributionsofdifferentpartsofthescatteringobjectstothetotaldiffracted
field.Detailedcommentsexplainallcriticalstepsintheanalyticandnumericcalcula-
tionstofacilitatetheirexaminationandutilizationbyreaders.Allchaptersarefollowed
by problems for independent investigations, which will be helpful in studying PTD,
especiallyfor students.
This book is intended for researchers working on antennas and scattering prob-
lemsinindustryanduniversitylaboratories.Itcanalsobeusefulforteachingavariety
ofuniversitycourses,thatincludetopicsonhigh-frequencyasymptotictechniquesin
diffractiontheory.Universityinstructorsandgraduatestudentswillbenefitfromthis
bookaswell.

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