Shinya Watanabe

Temperature distribution analysis of /spl lambda//4 type EM-absorber using resistive film

This paper describes the temperature distribution analysis of lambda/4 type EM-absorber using resistive film when high electric power is injected to the absorber. For the temperature analysis, FDTD method is used to analyze electromagnetics and SIMPLE (semi-implicit method for pressure linked equations) method is used for calculation of heat transport and air convection enabling to analyze local heat transfer more strictly than heat transport equation (HTE) method which is the traditional heat transport analysis method. And we propose four types of wave absorbers to analyze these temperature distribution on the resistive film to find the best type with least temperature rise. As a result, when glass and metal plates are used for spacer and reflector, respectively, the absorber proved to be the best one from a view point of temperature descent. And it is shown that the temperature range does not cause the change of absorbing characteristics in the analysis but the temperature rise exceeds 160 degC, the characteristics may change

Computer Simulation of Temperature Distribution of Frozen Material Heated in a Microwave Oven

In this study, the temperature distribution of a material (frozen tuna) that was heated in a commercial microwave oven is calculated by a coupled method using the finite-difference time-domain method, the semi-implicit method for pressure linked equations, the Monte Carlo method, and the radiative energy absorption distribution method. This method takes into consideration the melting heat during the phase change and the change in real and imaginary parts of the complex relative permittivity and heat conductivity during defrosting. Meanwhile, the temperature distribution of a sample of the frozen tuna is measured using an identical microwave oven and a thermograph. Then, the computed and monitored temperature distributions are compared. The calculated temperature distribution is found to agree well with the measured one, and the validity of the coupled method is confirmed. Additionally, the temperature distribution of a frozen heated material is verified both experimentally and theoretically.

Study of Temperature Distribution of λ/4 Type EM-absorber Using Resistive Film under High Power Injection

In this paper, first, FDTD, semi-implicit method for pressure linked equations (SIMPLE), Monte Carlo and radiative energy absorption distribution (READ) methods are combined to calculate electromagnetic field and all the heat transfer phenomena of heat transport, heat transfer by air convection and heat radiation (It is called FDTD-SIMPLE-MR method.). The temperature distribution of A/4 type EM-absorber using resistive film under high power injection is calculated using FDTD-SIMPLE-MR method. Next, the high power injection experiment is conducted using an absorber and high power RF instruments to get the temperature distribution experimentally. Finally, the calculated and measured temperature distributions of the absorber are compared. As a result, the calculated temperature distribution by FDTD-SIMPLE-MR method agrees well with the measured one and the validity of FDTD-SIMPLE-MR method is confirmed

Computer Simulation about Temperature Distribution of an EM-Wave Absorber Using a Coupled Analysis Method

Utilization of electromagnetic absorbers under high power is increasing. The absorbers are used in anechoic chambers for performance estimation of high power radars. Variation of the absorption characteristics of the absorbers under such conditions is expected, due to the generation of heat or temperature change. In this paper, first the temperature distribution of a λ/4 type EM-wave absorber under high power injection is examined using the coupled method. The coupled method can calculate the electromagnetic field and all of the heat transmissions (heat transport, heat transfer and heat radiation). Next, the power injection experiment is examined using the absorber and high power instruments to get the temperature distribution experimentally. Finally the calculated and measured temperature distributions of the absorber are compared and discussed.

Analytical and Experimental Examination of Defrosting Spots of Heated Frozen Material in a Microwave Oven

In this paper, temperature distribution of heated material (a frozen tuna) in a microwave oven is calculated by the method which combines FDTD for electromagnetic field calculation with heat transport equation considering melting heat and the nonlinear and rapid change of complex relative permittivity and heat conductivity during defrosting. As a result, the calculated temperature distribution of heated material agrees well with the measured one, and the validity of the combined method considering melting heat and the change of complex relative permittivity and heat conductivity is confirmed

Analysis of Absorbing Characteristics of One-Layer EM-Absorber Using CIP Method

In this paper, Constrained Interpolation Profile (CIP) method is applied to Maxwells equation including complex permittivity and permeability and the validity of CIP method applied to the equation is confirmed compared with the FDTD method. And the dependency on CFL (Courant-Friedrich-Lewy) condition, cell size and estimates of ∂e ∂x, ∂μ ∂x and ∂σ ∂x of the absorbing characteristics of one-layer EM-absorber are calculated using CIP method and compared with that by FDTD method. As a result, it is confirmed that the characteristics obtained by CIP method is different from that by FDTD method.

An examination of electromagnetic field using CIP and characteristic curve methods

In this paper, we propose a method for analyzing one dimensional electromagnetic field employing constrained interpolation profile (CIP) method, characteristics curve method and time splitting method incorporated into the EM field equation considering lossy dielectric and magnetic materials in the domain of analysis. And also, the proposed method is applied to multi-dimensional EM field analysis. As a result, the validity of the CIP method applying EM field to compare FDTD method is confirmed.

Measurement of complex permittivity of liquid at V band

It is well known that a dielectric constant is essential and has frequency dispersion. So, great numbers of dielectric constant measurement methods have been studied at many frequency bands. Recently, commercial frequency bands have shifted to higher frequency regions. There have been strong demands for a dielectric constant measurement method of a liquid in the millimeters wave region. For that purpose, we gave attention to a free space method, using a lens antenna and measured dielectric constants of ethanol at V band as an example. These results were in good agreement with values measured by a probe method. It was confirmed that the method is effective in permittivity measurement of a liquid in the millimeter wave band.

Analytical study of temperature distribution of one-layer EM-absorber using a lossy dielectric material

In this paper, first, FDTD, semi-implicit method for pressure linked equations (SIMPLE), Monte Carlo and radiative energy absorption distribution (READ) methods are combined to calculate electromagnetic field and all the heat transfer phenomena of heat transport, heat transfer by air convection and heat radiation (It is called FDTD-SIMPLE-MR method.). The temperature distribution of an one-layer EM-absorber using a lossy dielectric material under high power injection is calculated using FDTD-SIMPLE-MR method and a traditional method. And the both calculated temperature distributions of the absorber are compared. As a result, the more detailed temperature distribution of the absorber is obtained by FDTD-SIMPLE-MR method.

Study of temperature distribution of a pyramidal EM-wave absorber under high power injection

Utilization of electromagnetic absorbers under high power is increasing. The absorbers are used in anechoic chambers for estimation of performance of high power radars. Variation of the absorption characteristics of the absorbers under such condition is expected, due to the generation of heat or temperature change. In this paper, first temperature distribution of a pyramidal EM-wave absorber under high power injection is examined using the coupled method. The coupled method can calculate electromagnetic field and all of the heat transmissions (heat transport, heat transfer and heat radiation). Next, the power injection experiment is examined using the absorber and high power instruments to get the temperature distribution experimentally. Finally the calculated and measured temperature distributions of the absorber are compared, discussed and evaluated.