340 likes | 455 Vues
This document discusses the Spectral Domain Immittance (SDI) method, focusing on the representation of a finite current sheet as multiple infinite phased current sheets. It explores how to decompose the current into components that excite TMz and TEz plane waves. The document outlines the launching properties of these waves within an infinite medium, leading to the development of Transverse Equivalent Network (TEN) modeling equations. Additional examples illustrate the practical application of the approach, addressing the behavior of currents and fields in free space.
E N D
ECE 6341 Spring 2014 Prof. David R. Jackson ECE Dept. Notes 38
SDI Method (cont.) ks The finite current sheet is thus represented as a set of infinite phased current sheets: where This phased current sheet launches a pair of plane waves as shown below:
SDI Method (cont.) ks Goal: Decompose the current into two parts: one that excites only a pair of TMz plane waves, and one that excites only a pair of TEzplane waves.
SDI Method (cont.) Define: Launching of plane wave by source:
SDI Method (cont.) Proof of launching property: Consider an arbitrary surface current. An infinite medium is considered, since we are only looking at the launching property of the waves. At z = 0 we have that Note: This follows from the fact that the magnetic vector potential component Ax is an even function of z (imagining the current to be in the xdirection for simplicity here).
SDI Method (cont.) Hence
SDI Method (cont.) Two cases of interest:
SDI Method (cont.) Split current into two parts: Launches TEz Launches TMz
Transverse Fields H E TMz :
Transverse Fields (cont.) H E TEz :
Transverse Equivalent Network TEN modeling equations:
TEN (cont.) Source
TEN (cont.) Source
Source Model Phased current sheet inside layered medium
Source Model (cont.) so Hence Also Hence
Source Model (cont.) TMz Model:
Source Model (cont.) TEz Model: (derivation omitted)
Source Model (cont.) The transverse fields can then be found from
Source Model (cont.) Introduce normalized voltage and current functions: (following the notation of K. A. Michalski) Then we can write
Source Model (cont.) Hence
Example Find for z0 due to a surface current at z= 0, with The current is radiating in free space.
Example Decompose current into two parts:
Example (cont.) Hence
Example (cont.) TMz Model For z>0:
Example (cont.) TEz Model For z> 0:
Example (cont.) Hence where
Example (cont.) Substituting in values, we have: Hence or