• 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.5 no.5
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• pp.805-809
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• 1995

In order to widen the band-width of ferrite absorber, compositional effect on the complex permeability of Ni-Zn ferrite and the structure of grid absorber were studied. From the experimental results, we could determine the optimum composition composition of Ni-Zn ferrite and the structure of grid absorber. Also, we manufactured grid absorber and investigated its microwave absorbing characteristics. Calculation shows that the ferrite frid absorber suppresses reflection ${\leq}-20dB$ from 30 MHz to 700 MHz and the conventional ferrite tile absorber suppresses reflection ${\leq}20dB$ in the frequency range of 30 MHz-400 MHz. It was found that the microwave absorbing performance of the ferrite grid absorber was superior to the ferrite tile absorber.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1992.10a
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• pp.2-29
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• 1992

According to the increase of occupation density of microwave frequency band on use microwave environments have been congested extensively. For shielding unnecessary electromagnetic wave of preventing the electromagnetic wave reflection a good conductor a low resistive material or a lossy material is mainly used. As a method to measure the absorbing characteristics of microwave absorber the fundamental microwave measuring method can be used. There is however a big problem in measuring errors since the wavelength of microwave is very short especially as in the case as microwave absorber for RADAR. Therefore this research aimed to a converting adaptor of 20mm${\Phi}$ coaxial tube from a Type-N connector to 20mm${\Phi}$ coaxial tube and to use it for designing microwave absorber and evaluating absorbing characteristics. Furthermore the measurements of absorbing characteristics and material constants have performed and reviewed which were carried out by using the coaxial tube in the short type and by using rectangular waveguide respectively As a result the validity of the measured values have been confirmed.

• 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 Institute of Navigation
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• v.15 no.1
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• pp.1-9
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• 1991

The coaxial sample holder with 20mm in diameter and the adaptor from type N connector-to-20mm${\phi}$ coaxial tube are designed and manufactured which have been used for designing and measuring the fabricated microwave absorber. In addition, the measure in method of material constants of the microwave absorbers is described, which is focused on minimizing the error due to the sample's shapes, the fitting conditions, etc. After describing the design method of a single-layed microwave absorber, the microwave absorbers for X-band, C-band and S-band RADARs are designed and fabricated, respectively, which are composed of ferrite, carborn, and binder and have good performance. Futhermore, we develop the high performance microwave absorber in extremely wide-band type for RADAR, which is composed of different material and its mixing ratio and which could cover nearly from 4 to 10 GHz.

• 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.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1478-1480
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• 1994

In this paper, the microwave absorption properties of two layered absorber were evaluated. The two layer absorber were composed of Ni-Zn ferrite/rubber absorber and Ferroxplana/rubber absorber. The most absorption properties condition were obtained when the transforming layer and absorbing layer were Ferroxplana/robber absorber and Ni -Zn ferrite/rubber absorber. respectivity. The optimal thickness of the transforming and the absorbing layer were 4(mm) and 1(mm), respective1y.

• 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.

• Journal of electromagnetic engineering and science
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• v.19 no.2
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• pp.71-81
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• 2019

This paper presents a design methodology for wideband single-layered microwave absorbers with arbitrary absorption at the design center frequency using reactive Salisbury screens. The bandwidth of the absorber increases when the flatness of the reflection response at the design center frequency is maximized. Based on this observation, closed-form design formulas for wideband absorbers are derived. As they are scalable to any design frequency, wideband reactive screens can be systematically realized using two-dimensional periodic crossed-dipole structures patterned on a resistive sheet. Based on this method, a single-layered absorber with a 90% bandwidth improved to 124% of the design center frequency is presented. For the purpose of physical demonstration, an absorber with a design center frequency of 10 GHz is designed and fabricated using a silver nanowire resistive film with a surface resistance of 30 Ω/square. The measured absorption shows a good agreement with both the calculation and the electromagnetic simulation.