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In this article, an attractive resonant technique is devised for calculating the dielectric properties of arbitrary length material under test (ALMUT), which is partially filled inside a waveguide cavity sensor. The proposed technique exempts two major assumptions viz. the depolarization effect and the theory of images, which were neglected in earlier cavity perturbation methods. A numerical model of the depolarizing factor, which precisely considers the impact of the relative permittivity and the sinusoidal variation of the electric field, is also formulated. First, the technical modification and the numerical analysis are provided and after that, a new set of formulas for characterizing the complex permittivity of ALMUT is developed. The numerical results suggest the accuracy and validity of the scheme for a broad range of dielectric samples, including the typical case, i.e., the full-length dielectric sample. The novelty of the presented technique can be ascertained from the fact that it provides higher accuracy irrespective of the actual sample length when compared with standard cavity techniques. A few standard dielectric samples with the partially filled arrangement are measured using the WR90 cavity, and the results are compared with their corresponding values obtained using the earlier reported conventional and modified techniques. It is found that the results evaluated using the devised scheme are consistent and independent of the actual dimensions of ALMUT. On the other hand, error in estimated complex permittivity using the earlier reported approaches shows substantial dependence on the sample size. [ABSTRACT FROM AUTHOR]

A robust cavity technique is proposed to quite accurately measure the complex permeability of the magnetic materials, which gives promising results for arbitrary length samples. This technique takes into account many factors such as magnetic field correction inside the sample under test, the effect of demagnetization, and the image theory, which was not considered in past. In this paper, a numerical model of the magnetometric demagnetization factor is developed, which precisely considers the effects of the relative permeability of sample and the nonuniform magnetic field over sample volume. The sensitivity of proposed technique is better than conventional and recently modified technique assuming arbitrary length sample. The proposed scheme typically provides 98% accurate result for the sample length greater than $0.15\times $ the width of the rectangular cavity. The proposed method is quite novel and can be appreciated due to the fact that it gives higher accuracy for all the cases when compared with other standard cavity techniques. [ABSTRACT FROM AUTHOR]

The applications of magnetic composites in electromagnetic shielding, resonance imaging, and biomedical drug research are growing rapidly. Therefore, there is a huge demand to characterize these materials in order to obtain their dielectric and magnetic properties in the microwave frequency range. In this paper, a novel rectangular cavity method is proposed to obtain the complex permeability and permittivity of the test sample placed in the $E$ -plane of the rectangular cavity. The proposed method eliminates the need of physical relocation of a specimen in the $H$ -plane, which is usually required in the case of presently available methods to characterize the magnetic samples. The closed-form formula for this unified approach is developed from the first principle, and is later modified to consider some practical consideration. The proposed method is first numerically tested and verified for various standard samples, where the data are taken from the literature. Thereafter, the $X$ -band rectangular cavity is designed and fabricated to measure a number of available samples. The significance of the proposed approach can be appreciated from the fact that even for finite-size samples, the permeability and permittivity can be extracted with the typical errors of 5% and 2%, respectively. [ABSTRACT FROM AUTHOR]

A novel planar multilayered epsilon-near-zero (ENZ) tunnel sensor based on fully laminated surface integrated waveguide (SIW) technology is proposed for the microwave measurement of dispersive materials. The proposed sensor is designed and optimized using parametric analysis to obtain the multilayered ENZ tunnel dimensions. It is observed that the width of the upper tunnel of the designed two-tunnel sensor should be at least half of the SIW width of the actual SIW structure for the multiband operation. The complex permittivity measurement using the proposed sensor is possible at two frequencies with a single set of measurement data. The proposed method is based on perturbation of the squeezed electric field having constant magnitude and high intensity inside the multilayered ENZ tunnel, which eventually increases the sensitivity of the proposed sensor. The sensitivity and accuracy of the proposed sensor are tested using both the simulated and the experimented data. It is found that the proposed sensor is highly sensitive, and typically demonstrates 6% error under ideal conditions, thus making it a good candidate for the microwave measurement of dispersive materials. [ABSTRACT FROM AUTHOR]

A generalized cavity method relaxing the major assumptions of conventional cavity perturbation technique is presented for characterization of the powdered sample in the microwave frequency range. The unified method, which is based on the inverse optimization technique, eliminates the complexity of measurement caused due to the existence of sample holder and produces an accurate result. In this paper, an attractive numerical calibration approach is proposed in lieu of the practical calibration technique which usually requires either a set of standards or a number of reference samples. The sample holder especially made of borosilicate glass is designed to contain the powdered samples, and the X-band rectangular cavity is fabricated. For verification of the proposed technique, the pulverized alumina and polyethylene oxide with various packing fractions are measured using the fabricated cavity and the vector network analyzer. The dielectric constant of these samples is extracted using the proposed unified approach which is found to be in good agreement with the theoretical data obtained by Landau-Lifshitz and Looyenga model. The accuracy of the proposed generalized cavity method for powdered samples is found to be better than the conventional resonator methods available in the literature. [ABSTRACT FROM AUTHOR]

An improved rectangular cavity (RC) approach is proposed for the accurate complex permeability determination of materials in the microwave frequency band. The proposed approach assumes the bar-shaped magnetic specimen to be placed along the width of the cavity to increase the sensitivity of the measurement. A generalized closed-form formula is derived accordingly to determine the complex permeability of these bar-shaped samples in terms of the cavity parameters measured under both loaded and unloaded conditions. The proposed formula is found to improve the accuracy of the original RC approach where samples are placed in the $H$ -plane traversing the maximum width of the cavity for permeability measurement. The improvement in accuracy is facilitated by considering the sinusoidal magnetic field variation over the test sample, which is otherwise neglected in most of the earlier approaches. The modified formula is numerically tested for a number of samples having wide range of permeability variations, and the obtained results are typically 40% more accurate than the values obtained using the original formula. Finally, the synthesized magnetic samples, viz., the carbonyl iron-epoxy composite and the manganese ferrite, are measured by placing them inside the fabricated X-band cavity with the help of a vector network analyzer. The proposed approach is quite advantageous for magnetic materials as finite-size samples having sample to cavity volume ratio of less than 3e-3 can be characterized quite accurately with typical errors of 2% and 3% in the real and imaginary parts of the complex permeability, respectively. [ABSTRACT FROM PUBLISHER]

A novel cavity-based unified approach to measure the complex permittivity of dielectric samples placed in the E-plane of a rectangular cavity is presented. The proposed generalized cavity method is not limited to test specimens of smaller electrical dimensions, and requires two basic steps. The first step modifies the conventional cavity perturbation technique, where the effects of possible air gap between the cavity slot and the test specimen are also considered. The second step of the proposed approach employs a numerical optimization scheme, where the actual 3-D geometry of the fabricated cavity is simulated using the numerical field simulator, the Computer Simulation Technology (CST) Microwave Studio. The dielectric properties of the test specimen in this case are determined with the help of a MATLAB-based optimization routine, which calls the CST modules over the component object model interface and minimizes the error between the measured and the simulated scattering coefficients. The permittivity of the test specimen determined using the first step is provided as the initial guess to improve the convergence of the numerical optimization scheme. The proposed unified approach is validated by designing two rectangular cavities having different slot sizes operating in the TE107 mode. A number of standard dielectric samples are measured with the help of a vector network analyzer, and a very good agreement is observed between the measured permittivity values and the published data available in the literature having a typical error of less than 2% for samples of even larger dimensions. [ABSTRACT FROM PUBLISHER]