A broadband approach to estimate the relative permittivity of dielectric cuboids has been proposed for materials of weak frequency dispersive characteristic. Our method involves a numerical iterative scheme with appropriate initial values carefully selected to solve for the relative permittivity in a wide range of frequencies. Good agreements between our method and references have been observed for nylon and acrylic samples. An applicable range relation between the minimal thickness, the frequency range and the dielectric property of the material has also been discussed.

We propose a new swept-frequency measurement method for the electromagnetic characterization of materials. The material is a multilayer cylinder that pierces a rectangular waveguide through two holes in the narrow waveguide walls. The complex permittivity and permeability of the material are calculated from measured S-parameters as an inverse problem. To this aim, the paper develops a complete electromagnetic formulation of the problem, where the effects of material insertion holes are taken into consideration. The formulation is validated through the measurement of ferrite and water samples in the S-band.

A simple, low reflection, and highly-efficient pilot-plant scale microwave irradiation reactor for woody biomass pretreatment was fabricated. Pretreatment is an essential process for effective bioethanol production. The fabricated reactor consists of 8 microwave irradiators which are attached to a metal pipe. The woody biomass mixture which contains water and organic acid flows through the metal pipe and is heated by microwaves at a total power of 12,kW. To design the microwave irradiators, we used a 3D Finite Element Method (FEM) simulator, which was based on the measured complex permittivity data of the woody biomass mixture. The simulation results showed that the reflection coefficient $|S_{11}|$ from the reactor was less than -30,dB when the woody biomass mixture temperature was between 30$^{circ}$C and 90$^{circ}$C. Finally, we experimentally confirmed that the fabricated irradiation reactor yielded a microwave absorption efficiency of 79%.

Four calculation techniques for the Q-factor determination of resonant structures are compared on the basis of the influence of the VNA measurement uncertainty. The influence is evaluated using Monte Carlo calculations. On the basis of the deviation, the dispersion, and the effect of nearby resonances, the circle fitting method is the most appropriate technique. Although the 3dB method is the most popular technique, the Q-factors calculated by this method exhibit deviations, and the sign and amount of the deviation depend on the measurement setup. Comparisons using measurement data demonstrate that the uncertainty of the dielectric loss tangent calculated by the circle fitting method is less than a third of those calculated by the other three techniques.

In this paper, a new swept-frequency method for the measurement of the complex permittivity and permeability of materials is proposed. The method is based on the S-parameters measurement of a cylindrical material placed inside a rectangular waveguide, where the axis of the cylinder is perpendicular to the narrow waveguide walls. The usage of cylinders in measurement is beneficial because they are easy to fabricate and handle. A novel exact solution of the field scattered by the cylinder is developed. The solution is based on expanding the field in a sum of orthogonal modes in cylindrical coordinates. Excitation coefficients relating the cylindrical scattered field to the waveguide modes are derived, and are used to rigorously formulates the S-parameters. Measurement are performed in the S-band with two dielectric materials (PTFE, nylon), and in the X-band with one magnetic material (ferrite epoxy). The measurement results agree with those from the literature.

The waveguide-penetration method is a method to measure the electrical properties of materials. In this method, a cylindrical object pierces a rectangular waveguide through a pair of holes at the centre of its broad walls. Then, the complex permittivity and permeability of the object are estimated from measured S-parameters after TRL calibration. This paper proposes a new calibration algorithm for the waveguide-penetration method. Reference materials with known electrical properties are fabricated in cylindrical shapes to fit into the holes in the waveguide and are used as calibration standards. The algorithm is formulated using the property of equal traces in similar matrices, and we show that at least two reference materials are needed to calibrate the system. The proposed algorithm yields a simpler means of calibration compared to TRL and is verified using measurements in the S-band. Also, the error sensitivity coefficients are derived. These coefficients give valuable information for the selection of reference materials.

A circular cavity resonance method is improved to measure the frequency dependence of complex permittivity of a dielectric plate by using multimode TE0m1 with integer m. The measurement principle is based on a rigorous analysis by the Ritz-Galerkin method. A new circular cavity with lowered height is designed from a mode chart of a cavity to decrease the number of unwanted modes near the TE0m1 modes. A copper cavity having 20 GHz for the TE011 mode was constructed based on this design. For glass cloth PTFE, RT/duroid 6010 and FR-4 dielectric plates, the frequency dependences are measured from resonant frequencies for the TE0m1 (m = 1, 2, 3 ...) modes. These measured results agree well with ones measured by using the conventional four different size cavities with TE011 mode. It is verified that the designed cavity structure is useful to measure the frequency dependence of low loss dielectric plates.

The Waveguide-Penetration method is a permittivity measurement technique where a columnar object pierces a rectangular waveguide through a pair of holes at the center of its broad walls. The permittivity of the object is estimated from measured S-parameters . This paper demonstrates a scheme for analyzing permittivity measurement errors in the Waveguide-Penetration method. The sources of errors are categorized into systematic and random error sources. Systematic errors in the values of the sample and waveguide holes diameters, the effect of sample's length, and the influence of ambient temperature are investigated and corrected for. Potential random error sources such as imperfect TRL calibration elements, VNA thermal noise, sample loading, and test-port cable flexure are analyzed and their contribution to random errors are estimated.

This paper describes a nondestructive measurement method for complex permittivity of dielectric plates at 2 GHz, using a cylindrical cavity resonator. The resonator is divided into two parts at the center. Two dielectric plates are symmetrically loaded around the center of the cavity. These plates have high permittivity of 45. A dielectric plate specimen is clamped with these halves. The values of relative permittivity ε and loss tangent tanδ of the specimen are obtained from the resonant frequency and unloaded Q-value of TE011 mode. Measured results of various materials are compared with those values obtained at 3 and 10 GHz by other cavity resonator method. An edge effect is taken into account by a reference method, using measurement data of a sapphire plate. The errors of the present method are smaller than 1% and 2-310-5 for ε and tanδ, respectively.