• Smart Structures and Systems
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• 제7권5호
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• 대한화학회지
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• 제46권5호
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• pp.437-471
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• 2002

포토레지스트의 감도 증진은 광산 발생제로부터 발생되는 산에 의해 자동촉매분해가 일어나는 산 증식제를 화학 증폭형 포트레지스트에 첨가함으로써 얻을 수 있다. 본 연구에서는 이소프로필리덴 디시클로헥산올의 p스티렌술폰산 유도체를 산 증식제로 합성되고 그 성능을 평가하였다. 이러한 산 증식제로 합성한 4-hydroxy-4`-p-styrensulfonyloxy isopropylidene dicyclohexane(1), 4,4`-di-styrenesulfonyloxy isopropylidene dicyclohexane(2) 그리고 4-p-styrene-sulfonyloxy-4`-tosyloxy isopropylidene dicyclohexane(3)는 레지스트 공정온도에 대하여 충분한 열적 안정성을 나타내었다. 또한 이러한 산 증식제를 사용한 경우에 광산 발생제만 사용한 poly(tert-butyl methacrylate)film에 비교하여 2배에서 12배 정도의 감도 증진이 일어나 광화상 제조에 실용적으로 응용 할 수 있음을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제3권2호
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• pp.111-117
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• 2003

We propose a diode-based RF pre-distorter with various gain and phase characteristics, for non-linearity compensation of RF power amplifiers. This pre-distorter results in the removal of the diode- and configuration-dependent characteristics in the conventional diode-based RF pre-distorters. We have analyzed the operation principle of the proposed pre-distorter. The results show that gain and phase characteristics of the pre-distorter in all four quadrants are achieved. Several power amplifiers and test signals are used for verifying the performance of the proposed diode-based RF pre-distorter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.122-127
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• 2003

In this paper, an adaptive predistortion scheme is proposed to compensate nonlinear distortions caused by high power amplifiers (HPA) in OFDM systems. A complex Wiener-Hammerstein model (WHM) is used to describe input-output relationship of HPA with linear dynamics. The predistorter is directly identified by complex power series model with memory, which is an approximate inverse of the HPA expressed by the WHM. The effectiveness of the proposed adaptive compensation scheme is validated by numerical simulation for 64QAM-OFDM systems.

• 전기전자학회논문지
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• 제16권3호
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• pp.177-181
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• 2012

본 논문에서는 증폭기의 온도에 따른 균일한 출력특성을 구현하기 위한 개선된 보상특성을 갖는 증폭기용 온도보상회로를 제안한다. 제안된 온도보상회로는 직렬로 연결된 2개의 브랜치라인(Branchline) 결합기와 결합기 사이에 위치한 2개의 다이오드로 구성된다. 그리고, 회로의 주변온도에 따라서 저항값이 반비례하는 특서을 갖는 써미스터(Thermistor)와 써미스터를 포함하는 오피엠프(Operational amplifier, OP-Amp.)회로로 다이오드의 동작 특성을 조정함으로써 기존의 온도보상회로에 비하여 보다 효율적인 보상특성을 갖도록 설계하였다.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1077-1082
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• 2007

We present a micromechanical active amplifier, inspired from the principle of the outer hair cells in cochlea, amplifying both displacement and force. The present micromechanical active amplifier modulates the resonant carrier motion using the variable stiffness spring whose stiffness changes proportionally to the input motion. We design, fabricate, and characterize two types of the amplifiers A and B, each having the variable stiffness spring fur the maximum displacement gain and force gain, respectively. In the experimental study, the amplifier A shows the displacement gain of 5.62, which is 2.15 times larger than that of the amplifier 3. The amplifier B shows the force gain of 10.0, resulting in 1.26 times larger value compared to that of the amplifier A. We experimentally verify that the haircell-inspired micromechanical amplifiers are capable to amplify both displacement and force.

• 전자공학회논문지D
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• 제34D권7호
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• pp.23-29
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• 1997

The performance degradation of CMOS differential amplifiers due to hot carrier effect has been measured and analyzed. Two-state CMOS amplifiers whose input transistors are PMOSFETs were designed and fabriacted using the ISRC CMOS 1.5.mu.m process. It was observed after the amplifier was hot-carrier stressed that the small-signal voltage gain and the input offset voltage increased and the phase margin decreased. The performance variation results from the increase of the transconductances and gate capacitances of the PMOSFETs used as input transistors in the differential input stage and the output stage and also resulted from the decrease of their output conductances. After long-term stress, the amplifier became unstable. The reason might be that its phase margin was reduced due to hot carrier effect.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권2호
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• pp.276-279
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• 2015

This paper presents two 3-stage D-band stacked amplifiers developed in a $0.13-{\mu}m$ SiGe BiCMOS technology, employed to compare the conventional cascode topology and the common-base (CB)/CB stacked topology. AMP1 employs two cascode stages followed by a CB/CB stacked stage, while AMP2 is composed of three CB/CB stacked stages. AMP1 showed a 17.1 dB peak gain at 143.8 GHz and a saturation output power of -4.2 dBm, while AMP2 showed a 20.4 dB peak gain at 150.6 GHz and a saturation output power of -1.3 dBm. The respective power dissipation was 42.9 mW and 59.4 mW for the two amplifiers. The results show that CB/CB stacked topology is favored over cascode topology in terms of gain near 140 GHz.

• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.1-6
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• 2014

Superconducting quantum interference device (SQUID) is a sensitive detector of magnetic flux signals. Up to now, the main application of SQUIDs has been measurements of magnetic flux signals in the frequency range from near DC to several MHz. Recently, cryogenic low-noise radio-frequency (RF) amplifiers based on DC SQUID are under development aiming to detect RF signals with sensitivity approaching quantum limit. In this paper, we review the recent progress of cryogenic low-noise RF amplifiers based on SQUID technology.

• ETRI Journal
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• 제24권3호
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• pp.190-196
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• 2002

This paper presents millimeter wave monolithic microwave integrated circuit (MMIC) low noise amplifiers using a $0.15{\mu}m$ commercial pHEMT process. After carefully investigating design considerations for millimeter-wave applications, with emphasis on the active device model and electomagnetic (EM) simulation, we designed two single-ended low noise amplifiers, one for Q-band and one for V-band. The Q-band two stage amplifier showed an average noise figure of 2.2 dB with an 18.3 dB average gain at 44 GHz. The V-band two stage amplifier showed an average noise figure of 2.9 dB with a 14.7 dB average gain at 65 GHz. Our design technique and model demonstrates good agreement between measured and predicted results. Compared with the published data, this work also presents state-of-the-art performance in terms of the gain and noise figure.