• Journal of Biosystems Engineering
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• 제32권4호
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• pp.237-246
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• 2007

In this study, the microwave free-space transmission technique was used to measure the dielectric property of powdered food at microwave frequencies. The sample holder was designed and fabricated to transmit the microwave signals ranging from 1 to 15GHz. From the microwave propagation theory the equation expressing the dielectric property of powdered food was derived and validated by standard dielectrics. The dielectric property of powdered food such as wheat flour, coffee powder and milk powder was measured and analyzed. In the uniform range of bulk density of material, the real parts of permittivity of the food samples increased with the increase of moisture content, bulk density and temperature of the samples. The propagation properties such as attenuation and phase shift increased linearly as the moisture density of the food samples increased. As a measuring frequency of the moisture content, the X-band was recommended.

• 한국전자파학회논문지
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• 제16권2호
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• pp.228-234
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• 2005

준 마이크로파 대역용 전자파 노이즈의 흡수체로서 자성 복합 시트를 개발하였다. Fe-Si-Al 자성 분말을 attrition mill을 이용해 편상화한 후 이것을 polymer와 혼합 분산시켜 전자파의 입사 방향에 수직한 방향으로 배향된 자성 복합 시트를 제조하였다. Attrition milling 시간이 긴 편상 분말일수록 제조된 자성 복합체의 유전율은 증가하나 투자율은 다소 감소하는 경향을 보인다. 또한 오랜 시간 milling한 편상 분말일수록 임피던스 정합 주파수는 저주파 쪽으로 이동하나 정합 주파수에서의 전자파 흡수율은 감소한다. 이러한 결과들로부터 복합 자성체의 유전율과 투자율의 주파수 특성을 제어하여 1.4 GHz에서 -8.2 dB의 반사 손실 특성을 갖는 두께 1.0 mm의 노이즈 흡수 시트를 개발하였다.

• 한국전자파학회논문지
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• 제17권4호
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• pp.387-392
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• 2006

K-대역에서 동작하는 3.5 mm 동축형 감쇠량 표준기를 개발하고 그 측정 불확도를 평가하였다. 전력비 전달방식의 4개의 모듈로 구성된 이 표준기는 18 GHz부터 26.5 GHz까지의 광대역에서 동작하며 각 모듈은 약 20 dB의 감쇠량을 가진다. 측정 가능한 최대 감쇠량은 80 dB이고 이때의 확장 불확도는 약 95% 신뢰수준에서 0.01 dB이다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.39-44
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• 2005

A broadband DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by newly inserted the transmission lines in conventional Switched-T attenuator and the optimization of the transmission line parameters. Momentum was employed in design for an accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify performance stability against the MMIC process variation. The attenuator has been fabricated with 0.15 $\mu$m GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic range. High attenuation accuracy has been achieved over all attenuation range and full 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies.

• 한국항해학회지
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• 제21권4호
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• pp.29-38
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• 1997

Because of the result of a large use of electronic equipments, the occupation density of microwave frequency band is highly increased, and electromagnetic environment is getting more seriously bad. It is sometimes reported that electronic machines are not normally operated on account of the influence of undesired electromagnetic wave, which often gives fatal blow to even human life and thus becomes serious social problems. OATS(Open Area Test Site) is principally used to measure EMI or examine elelctromagnetic emission. Because of various restrictions we often build semi-anechoic chamber which has the function of OATS to measure EMI or EMS other than OATS. If the difference of the site attenuation between semi-anechoic chamber and OATS is within ${\pm}3dB$, the semi-anechoic chamber is recognized as adequate facility to measure EMI or EMS. Accordingly authors evaluate and analyze site attenuation due to absorbent materials, polarization, mutual coupling effects, etc. The calculated and the measured site attenuation in semi-anechoic chamber are compared. As a result good agreement is obtained.

• 한국광학회지
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• 제17권5호
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• pp.475-479
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• 2006

본 논문에서는 폴리머 링 광공진기를 이용하여 집적광학형 K-band용 마이크로웨이브 대역통과 필터를 제안하고 구현하였다. 특히, 열광학 효과를 이용하여 광공진기의 공진파장을 변화시킴으로써 대역통과 필터의 전달특성을 전기적으로 조절하였다. 측정된 필터의 중심주파수는 20 GHz, 소멸비는 약 15 dB, 3 dB 대역폭은 2 GHz, 그리고 Q값은 10이었다. 마이크로웨이브 필터에서 중심주파수의 출력특성을 27 dB범위 내에서 ${\sim}6.7dB/mW$로 조절할 수 있었다. 전기적으로 조절되는 전달특성을 갖는 이 필터는 마이크로웨이브스위치 등으로 응용할 수 있을 것으로 기대된다.

• 대한전자공학회논문지
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• 제5권3호
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• pp.31-39
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• 1968

외부자계가 가해진 냉프라즈마에서의 마이크로파 전파 특성을 측정하였다. 직류방전프라즈마는 두 전극판을 구형도파관에 삽입한것과, 또한 유리시설관을 구형도파관에 삽입한 것에서 이루어졌다. 마이크로파 전파방향, 방전관축, 외부자계는 각각 수직이고, 자속밀도, 방전유기, 기체압등이 증가할때 프라즈마를 전파하는 마이크로파의 감쇠 및 흡수는 증가함을 보았다.

• Journal of information and communication convergence engineering
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• 제14권3호
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• pp.153-162
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• 2016

Microwave and millimeter waves are considered suitable frequency ranges for diverse applications. The prediction of rain attenuation required the 1-min rainfall rate distribution, particularly for data obtained locally from experimental measurement campaigns over a given location. Rainfall rate data acquired from Korea Meteorological Administration (KMA) for nine major sites are analyzed to investigate the statistical stability of the cumulative distribution of rainfall rate, as obtained from a 10-year measurement. In this study, we use the following rain rate conversion techniques: Segal, Burgueno et al., Chebil and Rahman, exponential, and proposed global coefficient methods. The performance of the proposed technique is tested against that of the existing rain rate conversion techniques. The nine sites considered for the average 1-min rain rate derivation are Gwangju, Daegu, Daejeon, Busan, Seogwipo, Seoul, Ulsan, Incheon, and Chuncheon. In this paper, we propose a conversion technique for a suitable estimation of the 1-min rainfall rate distribution.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1051-1057
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• 2000

A traveling-wave CPW(coplanar waveguide) electrode with abruptly broken input/output-taper for LiNbO$_3$optical modulator was designed and fabricated. The electrical characteristics of traveling-wave electrode on z-cut LiNbO$_3$crystal with SiO$_2$buffer layers were measured by network analyzer. To confirm the possibility of the electro-optic modulator electrode, detailed calculations of the impedance, microwave effective index and attenuation constants are presented as a function of the microwave electrode thickness, but the buffer layer thickness is fixed as 1${\mu}{\textrm}{m}$. These characteristics are discussed from the viewpoint of the device optimization and are expected to be design guides for the LiNbO$_3$modulator’s electrodes.

• Journal of Magnetics
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• 제4권2호
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• pp.65-68
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• 1999

The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).