• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.241-246
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• 2018

In this study, we proposed a wideband frequency tunable metamaterial absorber using a switchable ground plane (SGP). We proposed two fire retardant or flame resistant 4 (FR4) substrate structures for the SGP. An SGP is placed at the middle layer, between the top pattern and the bottom ground plane. The SGP can either be made ground or reactive, by switching the PIN diode ON/OFF. As the frequency is determined by the substrate thickness, the frequency can be switched from the SGP. The proposed absorber is demonstrated by full-wave simulations and measurements. When the SGP is turned on, an absorptivity higher than 90% is achieved from 3.5 GHz to 11 GHz. When the SGP is turned off, an absorptivity higher than 90 % is achieved from 1.7 GHz to 5.2 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1038-1044
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• 2011

In this paper, the multichannel intermediate frequency transceiver for broadband multimedia system is designed and the experimental results are analyzed. Basic elements of the transceiver such as frequency synthesizer, amplifier, mixer, automatic gain control amplifier are introduced. The analysis technique described here applies not only to amplifier but also to any other nonlinear components such as mixers and frequency doubler. Through the investigation of the power spectrum density of the transmitted signal, the phase noise of the local oscillator is evaluated below 70 dBc/kHz. The frequency characteristics of the modulated signal is flat within the system bandwidth. Also the effects of adjacent channel interference and supurious emission are analyzed. And the function of automatic gain control amplifier is well operated.

• 한국컴퓨터산업교육학회:학술대회논문집
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• 2003.11a
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• pp.5-10
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• 2003

본 논문에서는 wavelet을 이용한 워터마크 삽입 시스템 구현을 제안한다. wavelet 변환 기법은 JPEG2000 이나 MPEG-4와 같은 차세대 데이터 압축 표준의 기본적 연산으로서 DCT연산에 비해 주파수 해상도와 시간해상도를 모두 만족시킨다. 제안한 시스템은 크게 DWT 변환모듈, 워터마크 삽입모듈, IDWT 복원모듈, Main Controller모듈로 구성된다. DWT 변환모듈은 Haar 웨이블렛 변환알고리즘을 기반으로 설계 됐으며 1차 신축을 통해 변환된 주파수 영역에서 중간주파수 대역(LH 및 HL)을 선택하여 워터마크를 삽입하는 워터마크 삽입 모듈, IDWT를 이용 신호를 복원하는 모듈, 전체시스템 구성 블록을 제어하는 Main Controller모듈로 구성된다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.65-70
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• 2001

This paper presents a Receiver MMIC for the CDMA terminal. The complete circuit is composed of Low Noise Amplifier, Down Conversion Mixer, Intermediate Frequency Amplifier and Bias circuit. The Bias circuit implementation, which allows for compensation for threshold voltage and power supply voltage variation are provided. The proposed topology has high linearity and low noise characteristics. Results of the designed circuit are as follows: Overall conversion gain is 28.5 dB, input IP3 of LNA is 8 dBm, input IP3 of down conversion mixer is 0 dBm and total DC current consumption is 22.1 mA.

• Journal of Ocean Engineering and Technology
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• v.3 no.2
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• pp.526-526
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• 1989

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.20-30
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• 1999

We have made the single side hand filter for the dual channel receiver which is a heterodyne receiver to observe the cosmic radio waves with 100GHz band ranged from 85GHz to 115GHz and 150GHz band ranged from 125GHz to 175GHz simultaneously. We have introduced the filter theory using the principle of the Martion-Puplett interferometer, which has the characteristics of rotated polarization. To reduce the loss of the transmission and beam coupling which are caused from the path difference associated with the intermediate frequency the design and the implementation have been intensely considered. The receiver needs two filters with different characteristics each other. Because each of them has the optimum positions as a function frequency at which the signal frequency is fed to mixer and the image frequency is rejected to the image termination load. The intermediate frequency and its band width have been also evaluated. We have measured the property of two filters using the vector network analyser and the beam measurement system which is made by us. The responses of the filter as a function of the position and the frequency are compared with the theory. It is shown that not only the measured values are very close to the theoretical values, but also the image rejection ratios are better than 22dB for both filters. Through successful observation using a dual channel receiver with two manufactured filters, the performance of the filters has finally verified.

• Journal of Oral Medicine and Pain
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• v.18 no.2
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• pp.107-119
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• 1993

저자는 다양한 저작방법에 따른 전측두근과 교근의 좌우균형성을 규명하기 위하여 정상 성인 27명을 대상으로 습관성 저작시, 양측 규칙 저작시, 우측 규칙 저작시 및 좌측 규칙 저작시에 근활성도와 근전도 power spectrum을 컴퓨터를 이용한 근전도 시스템을 이용하여 분석한 결과 다음과 같은 결론을 얻었다. 1. 습관성 저작시 우측 전측두근 및 교근 모두 좌측에 비하여 높은 근활성도를 보였다. (p<0.05). 2. 양측 규칙 저작시 우측 교근은 좌측에 비하여 높은 근활성도를 보였으나 (p<0.05), 전측두근에서는 좌우측 근활성도의 유의한 차이가 없었다. 3. 우측 규칙 저작시 우측 전측두근 및 교근 모두 좌측에 비하여 높은 근활성도를 보였다. (p<0.05) 4. 좌측 규칙 저작시 좌측 교근은 우측에 비하여 높은 근활성도를 보였으나 (p<0.05), 전측두근에서는 좌우측 근활성도의 유의한 차이가 없었다. 5. 저작시 전측두근고 교근의 중간주파수 경사도는 좌우측에서 유의한 차이가 없었다.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.25-30
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• 2000

The relation between the phase-shift profile for the intermediate frequencies and the Langmuir adsorption isotherm at the poly-$Pt/0.1\;M\;H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The suggested interfacial equivalent circuit consists of the serial connection of the electrolyte resistance ($R_S$), the faradaic resistance $(R_F)$ and the equivalent circuit element $(C_P)$ of the adsorption pseudocapacitance $(C_\varphi)$. The delayed phase shift $(\varphi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\varphi=-tan^{-1}[1/2{\pi}f(R_s+R_F)C_p]$. The phase-shift profile $(\varphi\;vs.\;E)$ for the intermediate frequency (ca. 6Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm (9 vs. E). The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-$Pt/0.1\;M\;H_2SO_4$ electrolyte interface are $1.8\times10^{-4}\;and\;21.4kJ/mol$, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.675-678
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• 2015

In this paper, we proposed a multi-function conversion block for microwave receiver. The proposed multi-function conversion block is composed of a broadband voltage controlled oscillator and a dual-mode mixer. Depending on whether the bias voltage is supplied, the first IF(Intermediate Frequency) output frequency(4,595 MHz/6,045 MHz) needed in microwave receiver is converted to 720 MHz and the another IF output frequency(720 MHz) for receiving Ku-band has the multi-functional operations of the dual mode that are bypass and attenuation without frequency conversion. Implementation and measurement results show that each intermediate frequency has conversion loss characteristic according to the LO power. The LO power conversion loss of 4,595 MHz at the LO levels from 2 dBm to 4 dBm is 13 dB, another of 6,035 MHz is 12 dB and the other of 720 MHz is 7.0 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.500-505
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• 2002

In this paper, a novel architecture of programmable divider with fifty percent duty cycle output and programmable dividing number has been proposed. Through HSPICE simulation, a 900MHz frequency synthesizer with proposed frequency divider has designed in a standard 0.25$\mu\textrm{m}$ CMOS technology. To verify the operation of proposed frequency divider, a chip had been fabricated using 0.65$\mu\textrm{m}$ 2-poly, 3-metal standard CMOS processing and experimental result shows that the proposed frequency divider works well. The designed voltage controlled oscillator(VCO) has a center frequency of 900MHz, a tuning range of ${\pm}$10%, and a gain of 154MHz/V. The simulated frequency synthesizer performance has a settling time of 1.5${\mu}\textrm{s}$, a frequency range from 820MHz to 1GHz and power consumption of 70mW at 2.5V power supply voltage.