Electromagnetic Analysis of Radiometer Calibration Targets Using Dispersive 3D FDTD

• Published in: IEEE transactions on antennas and propagation Vol. 60; no. 6; pp. 2821 - 2828
• Main Authors: Sandeep, S., Gasiewski, A. J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-06-2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorbents; Applied classical electromagnetism; Applied sciences; Calibration; Debye series; Dispersion; dispersive; Electromagnetic wave propagation, radiowave propagation; Electromagnetism; electron and ion optics; Exact sciences and technology; Finite difference methods; finite difference time domain (FDTD); Finite difference time domain method; Finite element analysis; Floquet modes; Fundamental areas of phenomenology (including applications); genetic algorithm; Genetic algorithms; geometrical optics; HFSS; Materials; Mathematical models; Microwave radiometry; Physics; Radiolocalization and radionavigation; radiometer calibration; Radiometers; spectral reflectivity; Studies; Telecommunications; Telecommunications and information theory; Three dimensional; Time domain; Time domain analysis; High precision; Wave interaction; Numerical method; Debye series; Electromagnetic interactions; genetic algorithm; Convolution; Wide band; Electromagnetic waves; radiometer calibration; Modelling; Recursion method; Radiometers; Dispersive media; Electromagnetism; Absorbent material; Finite difference time-domain analysis; Boundary conditions; Lossy medium; geometrical optics; Calibration; dispersive; Absorbing boundary condition; Perfectly matched layer; Three dimensional model; spectral reflectivity; Floquet modes; finite difference time domain (FDTD); Thermal analysis; Piecewise linearization; HFSS
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2012.2194679

Accurate electromagnetic and thermal analysis is essential for designing wideband radiometer calibration targets as well as for understanding the electromagnetic wave interaction with these highly absorbing structures. To serve this purpose, a three dimensional dispersive finite difference time domain (FDTD) engine has been developed. We present the various aspects associated with this FDTD formulation, including modeling of dispersive lossy media using piecewise linear recursive convolution (PLRC) and application of uniaxial perfectly matched layer (UPML) absorbing boundary condition and symmetry/periodic boundary conditions to provide high accuracy using moderate computational resources. Time domain modeling of the dispersive radar absorbent material is performed by fitting the measured complex permittivity and permeability data to a series of Debye like terms using genetic algorithm (GA) optimization. The broadband reflectivity spectrum of the calibration target is obtained by transient plane wave excitation. The reflectivity spectra of pyramidal calibration targets in the frequency range [6, 200] GHz is obtained and compared to the geometrical optics limit and a finite element solution. The spectrum depends significantly on the height to base ratio and coating thicknesses of the absorbent material.