Hasar, Ugur Cem; Ozturk, Gokhan; Kaya, Yunus; Bute, Musa; Karaaslan, Muharrem; Barroso, Joaquim J.; Ramahi, Omar M.; Ertugrul, Mehmet

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.

AtıfScopus10·WoS10·OpenAlex10

İncele

Hasar, Ugur Cem; Barroso, Joaquim José; Buldu, Gul; Bute, Musa; Kaya, Yunus; Karacali, Tevhit; Ertugrul, Mehmet

It is well recognized that near-field effects become dominant when the metamaterial (MM) is in resonance. In addition, any inaccurate information of the location of reference planes, and the effective length can seriously affect the accuracy of retrieved electromagnetic properties of MMs. By considering all these issues, in this research paper, we propose a retrieval method for reference-plane invariant and thickness-independent determination of electromagnetic parameters of MM slabs involving boundary effects. Our method first accomplishes determination of effective length of MMs and calibration-plane factors using scattering parameter measurements, aside the resonance region, of two identical MMs with different lengths. Our method then incorporates near-field effects in accurate retrieval of electromagnetic properties of MMs. The method is verified by scattering parameters simulated for a homogeneous conventional material and a weakly or negligibly coupled inhomogeneous MM slab made by two metallic concentric split-ring-resonators. Consequences of an inaccurate information of reference-plane transformation factors and the value of effective lengths and of noninclusion of near field effects on the retrieved electromagnetic properties are thoroughly discussed by way of few examples to substantiate the accuracy of the proposed method.

AtıfScopus15·WoS15·OpenAlex15

İncele

Hasar, Ugur Cem; Barroso, Joaquim José; Kaya, Yunus; Ertugrul, Mehmet; Bute, Musa; Catalá-Civera, José M.

A two-step measurement procedure has been proposed for measurement of complex permittivity of dielectric materials using one-port reflection measurements. In the procedure, as a first step, a graphical method is applied to analyze on the complex reflection-coefficient plane the general pattern of dielectric behavior of the sample. Then, as a second step, optimization algorithms are utilized for retrieving electrical properties of samples. The procedure requires measurement of complex reflection scattering parameters of at least two samples with different lengths. It has been validated by X-band measurements of three polyvinyl chloride samples with lengths 5, 10, and 20 mm.

AtıfScopus14·WoS13·OpenAlex15

İncele

Hasar, Ugur Cem; Barroso, Joaquim José; Bute, Musa; Kaya, Yunus; Kocadagistan, Mustafa Engin; Ertugrul, Mehmet

We propose a non-resonant-type method for reference-plane invariant and thickness-independent permittivity measurement of solid dielectric materials when there is no information from permittivity. To achieve this, we derive a branch-index-independent function and verify that it determines the sample thickness and permittivity without resorting to finding the correct branch index value for three different measurement scenarios: (a) measurements at closely separated frequencies of non-dispersive samples, (b) measurements at largely separated frequencies of non-dispersive samples, and (c) measurements at largely separated frequencies of dispersive samples. Via a differential uncertainty analysis, the effect of inaccurate sample thickness on permittivity determination is also presented for demonstration of the improvement achieved by our method. For validation, we measured the permittivity of an approximately 20 mm PTFE sample using the presented method and compared its result with those from other similar methods. From the comparison, we note that the accuracy of tested methods from literature drastically decreases when accurate information of sample thickness is not known (in addition to a further decrease in accuracy when correct transformation factors from reference-planes are not known a priori), while the accuracy of our method is not influenced.

AtıfScopus25·WoS22·OpenAlex25

İncele

Hasar, Ugur Cem; Bute, Musa; Barroso, Joaquim J.; Sabah, Cumali; Kaya, Yunus; Ertugrul, Mehmet

In this paper, we analyze wave propagation properties (transmitted, reflected, and absorbed powers) of composite multilayer structures consisting of bi-anisotropic metamaterial (MM) slabs and conventional isotropic materials. We also separately investigate the propagation properties of bi-anisotropicMMslabs and conventional materials to better interpret the results. We consider two different bi-anisotropic MM slab structures composed of only splitring- resonators (SRRs) and composing SRRs and a rod. In the analysis, we apply the well-known transfer matrix method to obtain transmitted, reflected, and absorbed powers of the composite structures. From the analysis, we note the following three important results. First, while the transmitted powers from forward and backward directions of the multilayer structure are identical (reciprocal feature), reflected (and absorbed) powers from forward and backward directions of the multilayer structure are different. This difference arises from reflection asymmetric nature of the bi-anisotropic MM slabs. Second, whereas the conventional material loss influences propagation characteristics aside resonance frequencies of bi-anisotropic MM slabs, bi-anisotropic MM loss worsens propagation properties of the multilayer structure at resonance frequencies of these slabs. Third, variations in (or determination of) electromagnetic properties of low-loss thin conventional materials in between two bi-anisotropic MM slabs can be realized at frequencies in which conventional materials demonstrate thickness-resonance effect.

AtıfScopus11·WoS11·OpenAlex13

İncele

Hasar, Ugur Cem; Barroso, Joaquim José; Kaya, Yunus; Ertugrul, Mehmet; Bute, Musa

We propose a new transmission-reflection method for measuring constitutive parameters of liquid samples inside an asymmetric measurement cell (a sample over a low-loss holder in vertical position inside an empty waveguide section). We derived reference-plane invariant expressions for constitutive parameters measurement of liquid samples from reference-plane dependent scattering parameters. In addition, we also applied a simple approach for unique determination of transformation factor and reference-plane distances. After, we also investigated how the performance of the proposed method could be improved by performing a differential uncertainty analysis. From this analysis, we found the following key results: (a) the accuracy of the proposed method could be enhanced for low-loss liquid samples by using thicker samples, and (b) the effect of constitutive parameters and the length of the (low-loss) sample holder on constitutive parameters measurements of liquid samples by the proposed method is a key parameter in increasing the accuracy of the measurements. Finally, we performed constitutive parameter measurements of distilled water and methanol to validate the proposed method and compared the proposed method with similar methods in the literature. From the measurements, we note that our method is especially useful for liquid sample measurements when the reference-plane transformation factors are not known a priori and/or if the measurements are carried out over a high frequency range.

AtıfScopus20·WoS19·OpenAlex22

İncele