Title:
Noninvasive Procedure for Measuring the Complex Permittivity of Resins, Catalysts, and Other Liquids Using a Partially Filled Rectangular Waveguide Structure
Author(s):
M. Jaleel Akhtar, Lambert E. Feher, Manfred Thumm
Source:
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
Vol./Issue/Date:
VOL. 57, NO. 2, FEBRUARY 2009
Year:
2009
Page(s):
458-471
Keywords:
Abstract:
A waveguide based noninvasive procedure to measure
the complex permittivity of epoxy resins and catalysts normally
employed in the composite industry is presented. The proposed
method combines an analytical approach with a numerical optimization
technique, and is based on the injection of the liquid
under test beforehand into a cuvette (disposable container)
with rectangular cross section. The cuvette filled with the liquid
specimen is positioned at the center of a WR-340 rectangular
waveguide for measuring the scattering coefficient data in the
-band. The approximate value of the complex permittivity
of the specimen is reconstructed from the measured scattering
coefficient data using the newly proposed analytical closed-form
relations. These analytical expressions are based on derivation of
the transcendental equation for the multilayered partially filled
waveguide structure using the transverse resonance method. In
order to determine quite accurate values of dielectric parameters
of the liquid specimen, the experimental setup is simulated with
the help of a 3-D full-wave electromagnetic field simulator and
accordingly theoretical values of the scattering coefficients are
computed. The complex permittivity of the liquid specimen in
this case is determined using an optimization algorithm, which
minimizes the error between the theoretical and measured values
of scattering coefficients. To avoid the local minima problem
commonly encountered with optimization routines and to increase
the convergence rate, the complex permittivity of the specimen
reconstructed using the analytical approach is used as the initial
guess. The applicability of the overall procedure is determined by
measuring a number of liquid specimens used in the composite
industry.
Document:
Reference Id:
424
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