Toshifumi Saito

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.

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.

Examination on Temperature Distribution of a Pyramidal EM-wave Absorber Under High Power Injection

In this research, temperature distribution of a pyramidal EM-absorber under high power injection is computed by a coupled method called FDTD-SIMPLE-MR method. In this method, both electromagnetic field and all the heat transmission phenomena such as heat transportation, heat transfer by air convention and heat radiation can be calculated. Moreover, temperature distribution of a pyramidal EM-absorber is examined experimentally by using high power RF instruments. Then both the computed and the experimetal results are compared and examined. Average temperature difference between these temperature distribution results in about 4 degrees.

Investigation on EM Wave Absorbers by Using Resistive Film with Capacitive Reactance

It is known that the thickness of the λ/4 type EM wave absorber having a resistive film with the capacitive reactance is thinner than 1/4 wavelength. This paper investigates EM wave absorbers using the resistive film with capacitive reactance. We introduced the impedance into the resistive film, and then clarified the relationship between the impedance and the matching thickness in the single layer EM wave absorber. Practically, we carried out to grasp the impedance of the resistive films, which were prepared using the conductive flake powder. As the results, we have proven that the matching thickness in the single layer EM wave absorber could be realized 0.17 λ - 0.09 λ in the frequency range from 2 GHz to 8 GHz by using these resistive films. We also fabricated the single resistive layer and the double resistive layers EM wave absorber using these resistive films for Dedicated Short Range Communications (DSRC) and wireless Local Area Network (LAN), in which the matching thickness could be reduced to 45% and 30%, respectively, as compared with the each absorber using the non-capacitive reactance.

Study of Temperature Distribution of an One Layer EM-wave Absorber Using a Lossy Magnetic Material under High Power Injection

Utilization of electromagnetic absorbers under high power is increasing, for estimation of performance of high power radars in anechoic chambers. Variation of the absorption characteristics of the absorbers under the condition is expected, due to the generation of heat or temperature change. Absorbers using lossy magnetic materials are used widely because the absorbers are typically thin, compared with absorbers made from lossy dielectric materials. If the absorbing layer is thin, it is considered that the temperature rise is higher because the heat capacity is small. Therefore, to know the temperature distribution of absorbers using lossy magnetic materials under high power injection is important. In this paper, the temperature distribution of a EM-Wave absorber using a lossy magnetic material is calculated by a coupled analysis method we proposed for electromagnetics and all the heat transmissions. The computed result is compared with the measured result. Finally, the calculated and measured results are compared and discussed.

Investigation on 10 m Semi Anechoic Chamber by Using Grid-Ferrite and Open-Top Hollow Pyramidal EM Wave Absorber

This paper investigates the 10m semi anechoic chamber using a new type hybrid EM wave absorber consisted of the grid-ferrite and the open-top hollow pyramidal EM wave absorber. We designed a new type hybrid EM wave absorber, which length could be slightly realized 65cm. The 10m semi anechoic chamber was constructed in the size of L21.5 m x W13.5 m × H8.9 m as the result of the ray-tracing simulation using this absorber. Then, the site attenuation in the constructed anechoic chamber was measured by using the broadband calculable dipole antennas. As the result, the maximum deviations between the measured site attenuation and theoretical calculated one were obtained within ±3.6 dB in the frequency range of 30 MHz to 300 MHz. It was confirmed the validity of a new type hybrid EM wave absorber. Moreover, it was confirmed that the measured results agree with the ray-tracing simulation results, in which the differences are about ±1.5 dB.

Study of the internal temperature of a λ/4 type EM-wave absorber under power injection

In this paper, first the temperature distribution of λ/4 type EM-absorber under high power injection is calculated using the coupled method. The coupled method can calculate electromagnetic field, and all the heat transmission phenomena of heat transport, heat transfer by air convection, and heat radiation. Next, the calculated and measured temperature distributions on the surface of the absorber are compared. As a result, the calculated distribution agrees well with the measured one. The internal temperature of the absorber is also obtained from the coupled method.

Temperature distribution of /spl lambda//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 λ/4 type EM-absorber using resistive film under high power injection is calculated using FDTD-SIMPLE-MR method and a traditional 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.

Realization of 3 m Semi Anechoic Chamber by Using Hybrid EM Wave Absorber Consisting of Composite Magnetic Material

This letter proposes the thinnest hybrid EM wave absorber using a composite magnetic material, which can be applied to the 3 m semi anechoic chambers. We experimentally designed a new hybrid EM wave absorber of the wedge shape, which was made from the ferrite powder, the inorganic fiber and binder. As a result, the length of this absorber could be realized only 6 cm, which was ascertained having the non-flammable. The 3 m semi anechoic chamber is constructed in the size of L9 m x W6 m x H5.7 m using this absorber, and then the site attenuation is measured according to ANSI C63.4 in the frequency range of 30MHz-1 GHz. As a result, the measured normalized site attenuation is obtained within ±3 dB to the theoretical normalized site attenuation.