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An extraction technique is proposed for electromagnetic characterization of metal-backed multilayer metamaterial (MM) structures demonstrating reflection-asymmetric property. It uses recursive scattering parameters for direct and reversed configurations of a multilayer structure. The algorithm was validated by comparing the extracted electromagnetic properties of multilayer structures composed of different MM unit cells with those determined by one-layer-only S-parameter methods. Two-layer and three-layer multilayer structures composed of MM slabs with C-shaped and $\Omega $ -shaped rings and an FR4 material were fabricated and measured for experimental validation. A sensitivity analysis was also conducted to quantitatively evaluate the performance of our method against a small air gap between the multilayer structures and the short-circuit termination and between adjacent MM slabs within these structures. Strong agreement was observed between the resulted obtained using our method and measurements. [ABSTRACT FROM AUTHOR]

An attractive extraction method has been proposed to determine all constitutive parameters of diagonal permittivity and permeability tensors in addition to the coupling term (a total of seven quantities) of omega-type bianisotropic metamaterial (MM) slabs. Noniterative (no need to use any numerical method) and less-requirement (scattering parameters of two modes only) features put our method to the forefront over other similar methods in the literature. A bianisotropic MM slab synthesized by the Drude and Lorentz models and another bianisotropic MM slab constructed by split-ring resonators are considered to validate and examine the accuracy of our method. Finally, additional analyses are performed to test dependencies of our method on incidence angle and the number of cells and to investigate whether it retrieves a unique solution. [ABSTRACT FROM AUTHOR]

We propose a powerful graphical method for evaluating the natural complex frequencies and amplitudes of the layered structures for their electromagnetic characterization. Its advantage is to show a pattern of the location of the natural complex frequencies so that it would be possible to examine how they can move for a possible error in the measurement system. The method is validated by a two-layered structure by comparing the natural complex frequencies and amplitudes computed by the proposed method and the inverse Fourier transform. It has been applied to monitor the effect of noise in a measurement system. [ABSTRACT FROM AUTHOR]

Microwave reflection properties of early age (one to nine days) engineered cementitious mortar specimens with a different water-to-binder ratio ($w/b$) and different sample placements during curing were measured by an open-ended waveguide probe, and then, the effect of these curing conditions on microwave reflection properties was investigated. From this analysis, we note the following important points. First, microwave reflection properties measured from any side of the mortar specimen with higher $w/b$ are, in general, greater than the corresponding properties measured from the same side of the mortar specimen with lower $w/b$ (the effect of free-water content of mortar specimens with higher $w/b$). Second, the inclusion of fly ash into mortar mixtures retards the crossover of reflection properties of mortar specimens with different $w/b$ values. Finally, curing conditions should be accounted for finding the correlation between the destructive compressive strength measurements and nondestructive microwave reflection properties. [ABSTRACT FROM AUTHOR]

The singular spectrum analysis (SSA) technique has been applied for the elimination of ripples in the measured phase constant ($\beta$) of transmission lines with small impedance mismatches by the line–line method. Compared with other postprocessing switching error (SW) procedure, the error correction (EC) technique, and the rolling average (RA) approach, it has been found that the SSA technique is more effective in removing the ripples of measured $\beta$ of reflecting and nonreflecting X-band and/or Ku-band waveguide straights with different lengths. As a metric for quantitative analysis, we computed the normalized root-mean-square-error (RMSE) and goodness-of-fit (GoF) values of the retrieved $\beta$ values. Better performances of the SSA technique over the SW procedure, the EC technique, and the RA approach are observed when the RMSE and GoF values are considered. Besides, the effect of artificial noise added to scattering parameters on the overall performance of the SSA technique in $\beta$ determination of symmetric reflecting and nonreflecting lines was examined. Furthermore, we investigated the roles of the window length and the number of principal components in the application of the SSA technique and then proposed a two-step procedure for $\beta$ extraction of dispersive lines considering their roles. [ABSTRACT FROM AUTHOR]

The ray-series (RS) method, which is practically more tractable and feasible than the transfer matrix (TM) method for the time-domain analysis, is examined and applied for investigation of temporal reflection and transmission responses of an N-layer structure for a plane wave incidence. These responses are represented by reduced reflection and transmission coefficients associated with unit step functions with different effective time periods and weightings depending on electromagnetic properties of the layers constituting the N-layer structure. Numerical and simulation analyses in line with the residue theorem and Bromwich integral were performed to validate our formalism and practically demonstrate its applicability for temporal analysis. [ABSTRACT FROM AUTHOR]

A method is proposed for unique and accurate permittivity ( \varepsilon r ) extraction of low-loss thin samples from reference-plane-invariant amplitude-only measurements without resorting to the information of explicit permittivity of a sample holder. Thanks to the amplitude-only measurements, it is possible to bypass the increased phase uncertainty of scattering parameters and retrieve unique \varepsilon r . An uncertainty analysis is followed to investigate improved accuracy attained by our method. Waveguide measurements at the $X$ -band are next conducted to measure \varepsilon r of polyethylene and polyvinyl chloride samples with different lengths (the sample holder is a soda-lime glass) for validation of the method and for comparison its accuracy with other methods. From the comparison, we note that reference-plane-dependent methods necessitate precise knowledge of sample location for accurate \varepsilon r retrieval. Besides, it is observed that while compared reference-plane-invariant techniques either require that the sample holder does not move while positioning the sample over it or produce more than one solution for \varepsilon r measurement of low-loss dielectric samples, our method removes these two problems. [ABSTRACT FROM PUBLISHER]

An effective method for extraction of electromagnetic properties of bianisotropic biaxial omega-type metamaterial (MM) slabs from waveguide measurements is presented. The method relies on measurements of S-parameters of two MM slab configurations (transverse and longitudinal) to extract electromagnetic properties endowed with strong bianisotropic coupling. An uncertainty analysis is performed for examining the effect of geometrical parameters of the longitudinal configuration on its resonance characteristic. For verification of the proposed method, constitutive parameters of a polyethylene sample are extracted at the $X$ -band (8.2–12.4 GHz). Then, the method is applied for extraction of electromagnetic properties of an MM slab (square split-ring resonators over FR4 substrate) using simulated and measured S-parameters for the two configurations at the $X$ -band. It is noted that extracted electromagnetic properties obtained from measured S-parameters are in good agreement with those obtained from simulated S-parameters except for a small frequency shift and magnitude change, which could arise from fabrication tolerances, air gaps present between MM cells, and local irregular surface of the longitudinal configuration. For completeness, it is analyzed whether extracted properties satisfy the locality conditions. [ABSTRACT FROM AUTHOR]

This letter proposes a correct and robust retrieval method for extraction of electromagnetic properties of Pasteur chiral metamaterial (MM) slabs having asymmetrical transmission properties when near-field effects are present. The ray-tracing method has been applied to derive underlying equations for semi-infinite reflection coefficients of these slabs. A U-shaped Pasteur chiral MM slab was considered as a test slab to examine the near field effects on extracted semi-infinite reflection coefficients. It is noted that near-field effects should be taken into account for correct electromagnetic properties of Pasteur chiral MMs especially around resonance regions. [ABSTRACT FROM AUTHOR]

A retrieval method is proposed for determination of electromagnetic properties of bianisotropic metamaterial (MM) slabs involving boundary effects from electric and magnetic surface susceptibilities. To achieve this, we derived two characteristic functions for wave impedances by the application of generalized sheet transition conditions from which electromagnetic constitutive parameters are determined using scattering (S-) parameters of a pair of slabs with different lengths. We applied our method for extraction of electromagnetic parameters of an $\Omega $ -shaped MM slab. From our analysis, we noted the following main results. First, when compared with other methods that do not consider boundary effects, we noted that our method retrieves reference-plane-invariant and thickness-independent electromagnetic properties provided that higher order wave interactions at interfaces are negligible when considering two separate pairs of MM slabs differing by the same length and when the accuracy of simulations (meshing size) is improved. Second, extracted constitutive parameters are in good agreement with the locality conditions over which our model is constructed. Third, extracted electric surface susceptibilities at interfaces are correspondingly greater than magnetic surface susceptibilities due to strong electric resonance of the $\Omega $ -shaped MM slab. [ABSTRACT FROM AUTHOR]

We present an error correction algorithm for extraction of reflection and transmission scattering (S-) parameters of a two-port device without resorting to a complete two-port calibration. It is shown that S-parameters of thru and nonreflecting line connections in addition to S-parameters of an unknown device (and its reversed orientation) are needed for extracting full S-parameters of the device. For validation, we performed simulations for a chiral metamaterial (transmission asymmetric) and carried out measurements of S-parameters of an asymmetrically loaded waveguide section (reflection asymmetric). [ABSTRACT FROM PUBLISHER]