• Journal of the Korean Ceramic Society
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• v.30 no.10
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• pp.823-828
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• 1993

The performance of ferrite composite microwave absorber has been evaluated as the matching frequency, the matching thickness and the band width. Especially, matching frequency is very important in application of microwave absorber because it determines operating frequency range. In this study, the ferrite composite microwave absorbers consisted Ni-Zn ferrite and Zn2Y ferroxplana were prepared in order to control matching frequency. Then, the variation of the material constants and microwave absorbing characteristics were investigated with various ferrite mixing ratio. The material constants of ferrite composite microwave absorber could be controlled by variation ferrite mixing ratio. Therefore, it was confirm that matching frequency of microwave absorber could be shifted by control of material constants.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.756-761
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• 2003

The microwave absorption properties of silicone, chloride polyethylene(CPE), and natural lacquer which is newly suggested in this study as a binder for composite microwave absorber were investigated to develop a superior microwave absorber. MnZn ferrite composite microwave absorbers mixed with them were prepared and their absorption property was investigated. A MnZn ferrite microwave absorber mixed with natural lacquer showed an excellent microwave absorption property in expanded frequency band.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.49-54
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• 1991

In this study the correlation between material constants and microwave absorbing characteristics of ferroxplana composite microwave absorber used in X-band was investigated. The real part of permeability(${\mu}_{r}'$) was decreased and the imaginary part of permeability(${\mu}_{r}"$) of ferroxplana composite was increased with increaing ferroxplana loading ratio(F/R). The frequency showing maximum attenuation was shifted to lower frequency with increasing absorber thickness. The absorber 2.6 mm thick showed good band width property and 3.2 mm thick showed good attenuation property. From the apphcation of ferroxplana composite's material constants to the region of material constants which satisfy broad band width, it is found that the absorbing characteristics were estimated quantitatively. Estabhshment of material constants' region which satisfies broad band width can make practical application to design of high performance ferrite microwave absorber.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.415-419
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• 1994

The material constants(the complex permeability and permittivity) of ferrite composite determine its microwave absorbing characteristics. Therefore, in order to improve the microwave absorbing characteristics, it is necessary to control the material constants of the ferrite composite. In this study, the method of improving microwave absorbing characteristics by control of permittivity of ferrite composite which has not satisfying matching condition in C-X band (4 GHz~12.4 GHz) was investigated. It was possible to control the permittivity by adjusting graphite loading ratio in the ferrite composite microwave absorber. It was also concluded that the control of permittivity of ferrite composite is effective method to improve the microwave absorbing characteristics.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.293-297
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• 1992

A proper combination of complex permeability and permittivity is necessary to produce the zero-reflection microwave absorber with an impedance matching. Increasing of dielectric permittivity and development of an impedance matching was investigated in ferrite-rubber composite specimens by addition of conducting materials. Graphite powder of high dielectric constant was added to the composite specimens to increase the permittivity. The precise estimation of graphite content to produce the matched-wave-impedance absorber at a given frequency can be made by using the numerically derived solution map of impedance matching. It was suggested that permittivity adjustment is an effective technique to obtained the microwave absorber with both good absorbing properties and small thickness as well.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1355-1357
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• 1997

In this study, the ferrite/rubber composite microwave absorbers mixed Ni-Zn ferrite and $Ni_2Y$ ferroxplana were prepared in order to control matching condion. The variation of the material constants($\dot{\varepsilon}$, $\dot{\mu}$) and microwave absorbing characteristics were investigated with various ferrite mixing ratio. The material constants of ferrite/rubber composite microwave absorber could be controlled by variation ferrite mixing radio. The matching frequency and thickness could be controlled with various ferrite mixing ratio.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1406-1408
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• 1994

In recently, there is growing demand for microwave absorbing matrial, and for the design method of microwave absorber. We developed a new method to design the matching frequency and matrial thick for ferrite/rubber composite absorber. Ni-Zn ferrite prepared with coprecipitation was compounded with silicon rubber, and, subsequently, pressed to ring specimen. The matrial constant of the ferrite/rubber composite absorber was used to design the matching frequency and matrial thick with matching map. In this study, we could predict matching condition from the design method. Foremore, using matching boundary map, we could also predict the condition of over 20[dB] attenuation.

• Journal of Magnetics
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• v.3 no.2
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• pp.64-67
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• 1998

Microwave absorbing properties of ferrite-epoxy composite (absorbing layer) attached on the carbon fiber polymer composite (reflective substrate) are analyzed on the basis of wave propagation theory. A modified equation for wave-impedance-matching at the front surface of absorbing layer including the effect of electrical properties of the quasi-conducting substrate is proposed. Based on this analysis, the frequency and layer dimension that produce zero-reflection can be estimated from the intrinsic material properties of the obsorbing layer and the substrate. It is demonstrated that the microwave reflectivity of carbon fiber composite has a strong influence on the microwave absorbance of front magnetic layer.

• Composites Research
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• v.27 no.6
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• pp.225-230
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• 2014

In this study, a novel microwave absorber which consists of a structural part, a resistive sheet, and a low dielectric layer is proposed. Unlike the conventional Salisbury screen, a newly proposed absorber is capable of a range of absorbing performance, from narrowband to broadband. In the case of the narrowband absorber, the fabricated absorber with optimized design parameters has a strong resonance at 9.25 GHz and reflection loss of -44 dB with satisfying the -10 dB absorption in whole X-band (8.2 GHz~12.4 GHz). For the broadband absorber design, the reflectivity was minimized in the considered frequency ranges. The designed absorber showed two weak resonances near 6.5 GHz and 16.5 GHz and satisfied the -10 dB absorption from C-band to Ku-band (4 GHz~18 GHz). The measured reflection loss of fabricated absorber was well matched with simulation results, though the measurement was only performed on X-band. For the Salisbury screen to be capable of broadband absorption, it should be stacked multiply in a structure known as the Jaumann absorber. However, for the microwave absorber presented here, broadband as well as narrowband capabilities can be implemented without a change of the structure.

• Composites Research
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• v.29 no.3
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• pp.98-103
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• 2016

This paper deals with the fabrication and verification of the microwave absorbing structure using semiconductive fiber reinforced composite. Two kinds of fiber were used to fabricate composites. Electromagnetic properties of the composites were measured by freespace measurement system over X-band. Two single slab absorbers and a double slab absorber were designed by thickness optimization method. Single slab absorbers did not show good microwave absorption performance because the permittivity is away from non-reflection curve. Double slab absorber complemented the limitations on single slab absorber and it showed good microwave absorption performance. Double slab absorber showed -43.9 dB loss near 10 GHz.