• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.232-237
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• 2003

We present the derivation of the loci of the reflection coefficient of a loaded transmission line on the Smith chart as the length of the transmission line is varied. The results show that the loci constitute a circle when the characteristic impedance of the transmission line differs from the normalizing one, whose center and radius are determined by the impedances of the load and the transmission line. The results can be used in the matching circuit design using microstriplines when line width and length should be compromised.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.22-24
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• 2012

Depending on the status of the engine oil, the dielectric constant is changed. Dielectric constant of oil is related to the characteristic impedance of the probe and the characteristic impedance of the probe determines the reflected signal. In this paper, we derive an equivalent circuit of the probe and using the dielectric constant obtained by measuring the capacitance, the theoretical reflection coefficient of the probe was calculated. In the results, if the engine oil is deteriorated, we can see that the reflection coefficient is increased.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.11a
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• pp.439-442
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• 2007

강인한 얼굴 인식 시스템을 만들기 위해서는 안경의 제거가 중요한 요소이다. 이를 위해서는 뛰어난 성능의 안경 검출 방법이 필수적이다. 본 논문에서는 안경의 유무 판단에 관한 새로운 방법을 제안한다. 영상은 조명 부분과 반사부분의 곱으로 이루어져 있다. 얼굴의 경우 안경 고유의 반사계수와 얼굴 고유의 반사계수가 다른 점에 착안하여 anisotropic smoothing 방법을 이용하여 입력 얼굴 영상에서의 반사 부분을 얻고, 이를 이용하여 안경의 반사 부분을 얼굴의 반사부분에서 검출한 뒤 이진화한다. 이후, 이진화 된 안경 픽셀 수를 이용하여 안경의 유무를 판단한다.

• The Journal of the Acoustical Society of Korea
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• v.27 no.3
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• pp.129-139
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• 2008

The purpose of the present work is to derive the reflection and transmission coefficients of $S_0\;and\;A_0$ mode Lamb waves in relation to the geometry of a rectangular notch when the waves propagate across the notch in an elastic plate. Firstly, the excitable modes of the Lamb wave were analyzed with respect to the plate thickness. The scattering phenomena were divided into three independent processes according to the boundary shape of the notch and the direction of the wave propagation. Linear equations for each process were derived with corresponding free or continuous boundary conditions to analyze the scattered waves. By the rule of linear superposition, the waves scattered at each process were summed for each mode. Then the steady-state reflection and transmission coefficients of the scattered waves were determined so that the difference of energy flux between the incident and the scattered waves would remain within 4%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.967-975
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• 2012

This paper presents a method to measure reflection coefficients of microwave devices or antennas based on time domain analysis with sampling oscilloscopes. The reflection coefficients were extracted by the Fourier transformation of echo pulses from devices with respect to the 20 GHz incident pulse signals. The three-error terms, which are commonly used for the correction of a microwave network, were determined using a 3.5 mm calibration kit. In addition, a modified error-correction model associated with a directional coupler for reflection coefficient measurements is introduced. The results were compared with those of measured with a commercial vector network analyzer.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.71-76
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• 2023

In this paper, a humidity sensor using a microstrip patch antenna(MPA) and polyvinyl alcohol(PVA) is studied. PVA is a polymer material whose permittivity changes with humidity, and a rectangular slot is added to the radiating edge of the MPA, which is sensitive to changes in electric field, in order to increase the sensitivity to changes in relative permittivity. After thinly coating the area around the radiating edge with the rectangular slot of the MPA fabricated on a 0.76 mm-thick RF-35 substrate with PVA, the changes in the resonant frequency and magnitude of the MPA's input reflection coefficient are measured when relative humidity is adjusted from 40% to 80% in 10% increments at a temperature of 25 degrees using a temperature and humidity chamber. Experiment results show that when the relative humidity increases from 40% to 80%, the resonance frequency of the antenna' input reflection coefficient decreases from 2.447 GHz to 2.418 GHz, whereas the magnitude increases from -7.112 dB to -3.428 dB.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.136-141
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• 2024

In this paper, a broadband inset-fed microstrip patch antenna operating at 10.525 GHz band was proposed. The proposed broadband inset-fed microstrip patch antenna consists of three narrow rectangular patches. At the center of the center patch, two symmetrical side patches were connected by a strip conductor and were arranged with their centers shifted in a perpendicular direction with respect to the center patch. For performance comparison, a conventional inset-fed square microstrip patch antenna was designed. Experiment results show that the frequency band of the measured input reflection coefficient with a voltage standing wave ratio less than 2 for the broadband inset-fed microstrip patch antenna was 10.036-11.051 GHz (9.63%), whereas that for the conventional inset-fed rectangular microstrip patch antenna was 10.306-10.772 GHz (4.42%). Therefore, the input reflection coefficient frequency bandwidth of the fabricated broadband inset-fed microstrip patch antenna was increased by 2.18 times, compared to the conventional inset-fed square microstrip patch antenna.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.265-268
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• 1998

본 논문에서는 1채널(mono)이나 2채널(stereo)의 오디오 입력을 5채널(center, left, right, left side, right side)로 출력시키는 음장 시스템을 설계하고 그 성능을 분석하였다. 가정의 리스닝 룸 같이 작은 공간에서 콘서트 홀 같은 커다란 공간의 음장을 재현하기 위한 멀티 채널 음장 시스템은 지연기, 초기 반사음처리기, 잔향기를 이용해 설계하였다. 초기 반사음 처리기의 지연과 이득은 실제 공간에서 측정한 암펄스 응답을 이용하여 결정하였으며, 구현된 초기 반사음을 전방 30$^{\circ}$방향에서 재생함으로써 확장감을 증가시킬 수 있도록 하였다. 잔향기는 자연스러운 주파수 및 감쇠 특성을 갖도록 설계되었으며, 후방 60$^{\circ}$방향에서 재생되는 잔향의 상관 계수를 작게 함으로써 청취시 공간감을 느끼게 하였다. 설계된 음장 시스템은 무향실 데이터를 입력으로 시뮬레이션되었고, 그 결과로 얻어진 5개의 PCM 출력은 멀티 트랙 재생 장치에 의해 일반 리스닝 룸에서 재생된다.

• The Journal of the Acoustical Society of Korea
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• v.29 no.4
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• pp.223-228
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• 2010

High-frequency bottom loss measurements for grazing angle of $82^{\circ}$ in frequency range 17-40 kHz were made in Jinhae bay in the southern part of Korea. Observations of bottom loss showed the strong variation as a function of frequency, which were compared to the predicted values using two-layered sediment reflection model. The geoacoustic parameters including sound speed, density and attenuation coefficient for the second sediment layer were predicted from the empirical relations with the mean grain size obtained from sediment core analysis. The geoacoustic parameters for the surficial sediment layer were inverted using Monte Carlo inversion algorithm. A sensitivity study for the geoacoustic parameters showed that the thickness of surficial sediment layer was most sensitive to the variation of the bottom loss.