• 한국항행학회논문지
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• 제21권6호
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• pp.626-632
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• 2017

본 논문은 삽입 손실이 작은 레디알 전력 결합기를 이용하여 낮은 전력의 증폭기 8개를 결합하여 고출력 증폭기를 구현한 것이다. 구현된 레디알 전력 결합기는 8개의 입력 포트를 갖고 있는 비공진형 특성을 갖고 있으며 마이크로스트립으로 구현하였고, 1.045 GHz 동작 주파수에서 확인한 결합기의 특성은 삽입손실 0.7 dB, 반사손실 12 dB 이상을 얻었다. 또한, 사용된 낮은 전력의 증폭기는 AFT27S010NT1 트랜지스터를 이용하여 설계하였으며, 동작 주파수에서 동일한 이득, 위상 및 일정한 출력 특성을 만족하도록 설계하였다. 제작된 레디알 전력 결합기와 8 W 출력의 드라이브 증폭기를 이용하여 낮은 전력의 증폭기 8개 구동시켜서 결합한 고출력 증폭기는 1.045 GHz 동작 주파수에서 33 W의 출력 특성을 얻었다. 또한, 낮은 전력 증폭기가 고장이 발생했을 때 레디알 결합기를 이용한 증폭기의 출력특성이 점진적으로 열화되는 결과를 확인하였다.

• 센서학회지
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• 제31권2호
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• pp.120-124
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• 2022

With advancements in underwater stealth technology for naval vessels, new sensor configurations for detecting targets have been attracting increased attention. Latest underwater mines adopt multiple sensor configurations that include electric field sensors to detect targets and to help acquire accurate ignition time. An underwater electric field sensor consists of a pair of electrodes, signal processing unit, and preamplifier. For detecting underwater electric fields, the preamplifier requires low-noise amplification at ultra-low frequency bands. In this paper, the specific requirements for low-noise preamplifiers are discussed along with the experimental results of various setups of matched transistors and chopper stabilized operational amplifiers. The results showed that noise characteristics at ultra-low frequency bands were affected significantly by the voltage noise density of the chopper amplifier and the number of matched transistors used for differential amplification. The fabricated preamplifier was operated within normal design parameters, which was verified by testing its gain, phase, and linearity.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.459-460
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• 2020

The design of a low distortion class E amplifier with a frequency of 6.78MHz for a wireless power transfer is presented. The amplifier with a differential out is designed to reduce the harmonics of the output current. The harmonic characteristics of various types of the class E amplifiers are compared through the simulation study.

• 한국통신학회논문지
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• 제17권1호
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• pp.68-79
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• 1992

고속 아날로그 시스템,위성통신시스템, video signal processing 및 processing 및 optical fiber interface 회로등에서 높은 전자이동도로 인하여 고주파 툭성이 우수한 GaAs 연산 증폭기는 필수적인 구성 요소이다. 하지만, 낮은 전달컨덕턱스 및 low frequency dispersion등의 현상 때문에 높은 전압이득을 얻을 수 없다는 단점을 가지고 있다. 따라서 본 논문에서는 GaAs MESFETfmf 이용한 증폭기의 이득을 증가시키기 위한 기법을 비교분석하고 기존의 전류미러와 새로운 구성의 전류 미러를 설계하여 회로의 안정화를 꾀하였다. 높은 차동전압이득을 얻기 위하여 단일 증폭기의 bootstrap 이득증가기법을 이용하여 차종입력 회로를 구성하였으며, 회로의 안정도 및 우수한 주파수 특성을 얻기 위하여 common mode feedback을 사용하였다. Pspice를 통한 시뮬레이션 결과 설계된 회로의 이득이 18.6dB 향상되었고 안정도 및 주파수 특성면에서 우수함을 확인할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제19권3호
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• pp.135-140
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• 2019

본 논문에서는 L, S 및 C 대역에서 동작하는 주파수 분배 방식의 광대역 구동증폭기를 설계 및 제작하였다. 구동증폭기의 비대역폭이 100% 이상인 경우에는 트랜지스터를 효율적으로 이용하기 어려우며, 특히 주파수 대역에 따라 출력 전력 및 효율의 특성이 민감하게 변하는 전력증폭기를 동작시키기 위해서는 구동증폭기의 특성이 중요하게 작용한다. 본 논문에서는 구동증폭기의 대역폭을 최대화하고, 구동증폭기의 뒤쪽에 위치 할 전력증폭기의 트랜지스터를 효율적으로 이용 할 수 있도록 구동증폭기의 출력을 저대역과 고대역으로 나누어주는 주파수 분배 방식을 적용하였다. 설계된 회로는 GaAs HBT (Heterojunction Bipolar Transistor) 공정 및 9-layer의 SiP (System in Package)를 이용하여 제작하였고, 측정을 통해 성능을 검증하였다. 제작된 회로는 동작 주파수 범위에서 8 dB이상의 이득과 15 dBm이상의 출력전력을 보여주었다.

• ETRI Journal
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• 제36권3호
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• pp.510-513
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• 2014

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency ($F_{OP}$) and short circuits at an image frequency ($F_{IM}$). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and $F_{IM}/F_{OP}$ of the reported millimeter/quasi-millimeter wave IR-LNAs.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.191-194
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• 1999

The balanced amplifier is a practical amplifier to, implement a broadband amplifier that has flat gain and good input and output VSWR. Three-stage amplifier design procedure usually divided into three partition satisfying the following requirements : low noise figure, high gain and high power output. FHX35LG HEMT device is used in the design can be obtained low noise figure at the first-stage, MGA82563 MMIC device is used in the design can be maintained high gain at the second-stage, and AHI MMIC device is used in the design can be required high power output at the third-stage. The results of three-stage balanced amplifier show that power gain is about 40㏈, noise figure is less than 1.2㏈ at operating frequency.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.2-6
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• 2000

We have developed an extremely sensitive radio frequency amplifier based on the dc superconducting quantum interference device (dc SQUID). Unlike a conventional semiconductor amplifier, a SQUID can be cooled to ultra-low temperatures (100 mK or less) and thus potentially achieve a much lower noise temperature. In a conventional SQUID amplifier, where the integrated input coil is operated as a lumped element, parasitic capacitance between the coil and the SQUID washer limits the frequency up to which a substantial gain can be achieved to a few hundred MHz. This problem can be circumvented by operating the input coil of the SQUID as a microstrip resonator: instead of connecting the input signal open. Such amplifiers have gains of 15 dB or more at frequencies up to 3 GHz. If required, the resonant frequency of the microstrip can be tuned by means of a varactor diode connected across the otherwise open end of the resonator. The noise temperature of microstrip SQUID amplifiers was measured to be between $0.5\;K\;{\pm}\;0.3\;K$ at a frequency of 80 MHz and $1.5\;K\;{\pm}\;1.2\;K$ at 1.7 GHz, when the SQUID was cooled to 4.2 K. An even lower noise temperature can be achieved by cooling the SQUID to about 0.4 K. In this case, a noise temperature of $100\;mK\;{\pm}\;20\;mK$ was achieved at 90 MHz, and of about $120\;{\pm}\;100\;mK$ at 440 MHz.

• Progress in Superconductivity
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• 제2권1호
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• pp.1-5
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• 2000

We have developed an extremely sensitive radio frequency amplifier based on the dc superconducting quantum interference device (dc SQUID). Unlike a conventional semiconductor amplifier, a SQUID can be cooled to ultra-low temperatures (100 mK or less) and thus potentially achieve a much lower noise temperature. In a conventional SQUID amplifier, where the integrated input coil is operated as a lumped element, parasitic capacitance between the coil and the SQUID washer limits the frequency up to which a substantial gain can be achieved to a few hundred MHz. This problem can be circumvented. by operating the input coil of the SQUID as a microstrip resonator: instead of connecting the input signal between the two ends of the coil, it is connected between the SQUID washer and one end of the coil; the other end is left open. Such amplifiers have gains of 15 dB or more at frequencies up to 3 GHz. If required, the resonant frequency of the microstrip can be tuned by means of a varactor diode connected across the otherwise open end of the resonator. The noise temperature of microstrip SQUID amplifiers was measured to be between 0.5 K $\pm$ 0.3 K at a frequency of 80 MHz and 1.5 K $\pm$: 1.2 K at 1.7 GHz, when the SQUID was cooled to 4.2 K. An even lower noise temperature can be achieved by cooling the SQUID to about 0.4 K. In this case, a noise temperature of 100 mK $\pm$ 20 mK was achieved at 90 MHz, and of about 120 $\pm$ 100 mK at 440 MHz.

• 전기의세계
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• 제29권12호
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• pp.798-803
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• 1980

A computer program for noise analysis of the audio circuit is developed. The application of the program to the equalizer, low frequency amplifier of radio circuit and cascaded amplifier show good results. The general noise analysis method for cascade operational amplifier is presented. The noise spectral power density is calculated for a resonator active filter.