Measurement of Mode Patterns in a High-Power Microwave Cavity

A wet thermal paper method for measuring of mode patterns and heat distributions in a high-power microwave multimode cavity is developed. The exposure time of the paper is evaluated. It is shown that this method allows measuring and recording mode patterns in the loaded and unloaded cavity, and the heat distribution inside the cavity with a load movement. The mode patterns and heat distributions along horizontal and vertical planes of the cavity are presented. Possible applications of the method in medicine and biology are discussed, and a calibration protocol of a microwave oven for microwave radiation exposure on cell cultures in the cavity is given

Measurement and Monitoring of Microwave Reflection and Transmission Properties of Cement-Based Specimens

The results of measurement and monitoring of reflection and transmission properties of cement-based specimens (blocks of mortar, concrete) during long time of their service lives, including hydration process, and different curing conditions at microwave frequencies (X-band) are presented. A simple and inexpensive measurement system that utilizes the nondestructive and contactless free space method is used. Dependencies of the reflection and transmission coefficients on water-to-cement ratio, preparing and curing conditions of the specimens are demonstrated. It is shown that the reflection coefficient is approximately stable after hydration process while the transmission coefficient changes during long time of the specimen\u27\u27s service life. The complex dielectric permittivity of the cement-based materials is calculated by a new method using only the amplitudes of the reflection and transmission coefficients. The expected applications of the results are discussed

Measurement and Monitoring of Microwave Reflection and Transmission Properties of Cement-Based Specimens

The results of measurement and monitoring of reflection and transmission properties of cement-based specimens (blocks of mortar, concrete) obtained by using a simple and an inexpensive measurement system at microwave frequencies (X-band) are presented. Dependencies of the reflection and transmission coefficients on water-to-cement (w/c) ratio, preparing and curing conditions of the specimens are demonstrated. It is shown that the amplitudes of reflection and transmission coefficients, together with thickness of the specimens, determine the complex dielectric permittivity of the hardened cement-based specimens. The expected applications of the results for the determination of physical properties of cement-based materials are discussed. The causes and effects of measurement errors and uncertainties are also discussed

Measurement and Monitoring of Microwave Reflection and Transmission Properties of Cement-Based Materials for Propagation Modeling

A non-destructive, contactless, free-space method is used for measuring and monitoring the properties of cement-based materials. We analyse the propagation factor, penetration depth and reflection and transmission coefficients of the plane wave interacting with the highly lossy specimen. Results are presented of the measurement and monitoring of the properties of cement-based materials during all stages of their lives and different curing conditions The expected applications of the results for propagation modelling are discussed

Determination of complex dielectric permittivity of loss materias at microwe frequencies

The method of determination of complex dielectric permittivity of loss materials at microwave frequencies (X-band) using measured amplitudes of reflection and transmission coefficients and numerical calculations is developed. Different numerical methods namely graphical, bisection (halving), newton, and secant, are applied in order to determine the permittivity of cement-based materials. Simulation time and errors of these methods are compared. It is shown that the fastest and most accurate method is the bisection (halving) method because it is a global method.The method of determination of complex dielectric permittivity of loss materials at microwave frequencies (X-band) using measured amplitudes of reflection and transmission coefficients and numerical calculations is developed. Different numerical methods namely graphical, bisection (halving), newton, and secant, are applied in order to determine the permittivity of cement-based materials. Simulation time and errors of these methods are compared. It is shown that the fastest and most accurate method is the bisection (halving) method because it is a global method

Reference-plane-invariant and thickness- and branch-index-independent retrieval of effective parameters of bi-anisotropic metamaterials

We propose a retrieval method for reference-plane-invariant electromagnetic parameter measurements of bi-anisotropic metamaterial slabs without resorting to accurate information of the slab thickness and the branch index. To extract reference-plane distances, the slab thickness, and the branch index, we first approximate wave impedances and refractive index away from the slab resonance frequency and then use scattering parameters to calculate the refractive index and the branch index. Once these quantities are determined, they are used as inputs for the retrieval of electromagnetic properties of slabs over the whole band. Different approximations for refractive index and wave impedances are applied to demonstrate the applicability and accuracy of our proposed method. We tested our method for electromagnetic parameter extraction of bi-anisotropic split-ring-resonator and Omega-shaped MM slabs with different number of unit cells. From our analysis, we note that inaccurate information of reference-plane distances, the slab length, and the branch index not only changes the amplitude but also shifts the response of the electromagnetic properties. We show that the presented method can be applied for accurate electromagnetic parameter extraction of bi-anisotropic MM slabs