J. KIMS Technol Search


Journal of the Korea Institute of Military Science and Technology 2003;6(2):73-82.
A Free-Space Method for Measurement and Analysis of Dielectric Characteristics of Electromagnetic Absorbing Materials at Microwave Frequencies
자유공간 기법을 적응한 마이크로파 대역 전파흡수재의 유전 특성 분석
For measurements and analysis of dielectric characteristics of planar slabs of microwave absorbing materials, I have applied a free-space method in the frequency range of 8~14 GHz. The measurement system for free-space method consists of transmit and receive antennas, mode transitions, precision coaxal cables, the network analyzer, and a computer Special Spot-focused horn lens antenna was used to eliminate diffraction effects. Diffraction effects at the edges of the sample are minimized by satisfying the condition for minimum transverse dimension of the plate and the beamwidth of the antennas at the focus. The time-domain gating feature of the network analyzer and the thru, reflect, and line(TRL) calibration technique were used to eliminate the effects of undesirable multiple reflections. The complex coefficients of reflection and transmission, $S_{11}$ and $S_{21}$, of planar samples were measured for standard materials such as Teflon, Rexolite$ extregistered$ 2200. The results were compared with existing measurement method. And I applied a free-space method for measurement to measure dielectric constants of some electromagnetic absorbing materials. Dielectric properties for the same samples were also measured with a 7mm coxial transmission line method for purposes of comparison with the free-space method.
Key Words: Free-space method, Diffraction effects, Complex dielectric constant, Multiple reflection, TRL(Through, Reflect and Line), 7mm coxial transmission line method
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