Free space material characterization using genetic algorithms

Abstract

This work demonstrates the use of genetic algorithms (GA) to transform the traditional free space characterization process into an optimization process. The basis of the process is to compare the measured reflection coefficient to the reflection coefficient computed by the GA. The GA computes the reflection coefficient using candidate solutions of the permittivity and permeability and the Fresnel reflection coefficient equations. The permittivity and permeability that yield the reflection coefficient closest to the measured reflection coefficient is determined to be the best solution. Results using synthetic reflection coefficient data using a Plexiglas sample show accurate extraction of the permittivity with both transverse electric and transverse magnetic polarized plane waves.

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“…The resonant frequency of the measurement and the model one matched considering e 0 r 5 4.38. To match experimental curves with numerical simulations curves is a classical method to calculate the electromagnetic properties [18].…”

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“…6, Liu & Pu introduced a concept of microwave chemistry using a novel MRR to measure complex permittivity of liquid. Subsequently, they are now common technology for filters design [7][8][9][10][11][12][13][14][15][16], antenna [16][17][18][19], and finally in oscillator circuits [20]. Seeing the proposed MRRs consist of sub-wavelength linear impedance sections of about quarter wavelength length, interaction between these components has been difficult to analyses in order to achieve accurate characterization as an ideal subwavelength linear impedance section is not realizable at lower frequencies because of the associated parasitic reactance due to fringing fields particularly by virtue of their electrical and physical lengths on assumption that: (1) the voltage across the linear impedance sections is constant at any point in the line, (2) the current just before and beyond the section are equal, which inadvertently leads to an infinitely short impedance sections [21].…”

“…The resonant frequency of the measurement and the model one matched considering e 0 r 5 4.38. To match experimental curves with numerical simulations curves is a classical method to calculate the electromagnetic properties [18].The gain is measured at the point h 5 08 and u 5 08. Figure 8 shows the experimental data and results from numerical model.…”