Abstract
A microwave free-space reflection method for determining the complex permittivity of planar materials is demonstrated. Improved the MUltiple SIgnal Classification (MUSIC) algorithm to estimate the complex relative permittivity of material based on the reflection coefficients measurement of a metal-backed material sample placed in a free-space with the thickness of the samples is the much greater time the wavelength. The measurement system consists of a pyramidal horn antenna operating at X-band and a metal-backed sample placed in a free-space. From the measured values of the reflection coefficients through a known thickness of a planar slab of the material sample, the complex relative permittivity of the material samples is estimated by the proposed algorithm without determining an integer time the wavelength in the sample under test. The proposed algorithm is verified with different thickness material samples at X-band. The estimation results show that the complex relative permittivity of material samples is accurately when thickness changes.
Highlights
Permittivity is a physical quantity that describes how a dielectric material responds to an electric field
In our previous work [18], a proposed method to estimate the complex permittivity of the material samples placed in free space is carried out by a measurement system that consists of a transmitting and a receiving horn antennas to calculate transmission coefficient (S12 or S21) electromagnetic wave propagation in free space
The estimation results show that the complex relative permittivity of material samples is accurately when thickness changes as Fig. 8 and Fig. 9, Fig. 10 and Fig. 11, respectively, show the root mean squared error (RMSE) versus the thickness graph calculated from the simulation results for the three samples at different thicknesses
Summary
Permittivity is a physical quantity that describes how a dielectric material responds to an electric field. Several methods to measure the complex permittivity of dielectric materials have been developed Among these methods, the methods for determining the parameters of material using microwave propagation in free-space are nondestructive, contactless, and sample preparation requirements are minimal. The methods for determining the parameters of material using microwave propagation in free-space are nondestructive, contactless, and sample preparation requirements are minimal They are especially suitable for measurement of the complex permittivity and complex permeability of materials under high-temperature conditions [1], [2]. The free-space methods are based on the measurements of the phase of the reflection (S11) and transmission (S21) coefficient through a known thickness of the material samples.
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