• 전자공학회논문지D
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• 제34D권10호
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• pp.14-23
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• 1997

An MMIC downconverting mixer for cellular phone application has been successfully developed using an MMIC process including $1 \mu\textrm{m}$ ion implanted gaAs MESFET and passive lumped elements consisting of spiral inductor, $Si_3N_4$ MIM capacitor and NiCr resistor. The configuration of the mixer presented in this paper is single-ended dual-gate FET mixer with common-source self-bias circuits for single power supply operation. The dimension of the fabricated circuit is $1.4 mm \times 1.03 mm $ including all input matching circuits and a mixing circuit. The conversion gian and noise figure of the mixer at LO powr of 0 dBm are 5.5dB and 19dB, respectively. The two-tone IM3 characteristics are also measured, showing -60dBc at RF power of -30dBm. Allisolations between each port show better than 20dB.

• Journal of Communications and Networks
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• 제4권2호
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• pp.97-101
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• 2002

Based on their shift and scale orthogonality properties, scaling and wavelet functions may be used as signaling functions having good frequency localization as determined by the fractional-out-of-band power (FOOBP). In this paper, application of Daubechies' wavelet and scaling functions as baseband signaling functions is described, with a focus on finding discretely realizable pulse-shaping transfer function circuits whose outputs approximate scaling and wavelet functions when driven by more conventional digital signaling waveforms. It is also shown that the inter-symbol interference (ISI) introduced by the approximation has negligible effect on the performance in terms of signal-to-noise ratio (SNR). Moreover, the approximations are often more bandwidth efficient than the original wavelet functions. These waveforms thus illustrate an example solution of a tradeoff between residual ISI and bandwidth efficiency as a signal design problem.

• Advances in aircraft and spacecraft science
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• 제9권3호
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• pp.243-261
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• 2022

Broad writing on the examination of sandwich structures mirrors the significance of incorporating thermal loadings during their investigation stage. In the current work, an endeavor has been made to concentrate on sandwich FGM beams' bending behaving under thermal loadings utilizing shear deformation theory. Temperature-dependent material properties are used during the analysis. The formulation includes the transverse displacement field, which helps better predict the behavior of thick FGM beams. Three-different thermal profiles across the thickness of the beam are assumed during the analysis. The study has been carried out on both symmetric and unsymmetric sandwich FGM beams. It has been observed that the bending behavior of sandwich FGM beams is impacted by the temperature profile to which it is subjected. Power-law exponent and thickness of core also affect the behavior of the beam.

• 한국정보기술학회 영문논문지
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• 제10권1호
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• pp.99-109
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• 2020

As environmental pollution has become severe due to the rapid increase in pollutant generation in the air, measurement, collection, and analysis of atmospheric environment information plays an important role. However, it is difficult to measure the high-resolution and real-time atmospheric environment of the cities and tourist spots with high population mobility only by measuring equipment of stationary measuring stations. Therefore, this paper proposes a portable atmospheric environment measurement system for real-time measurement and monitoring of atmospheric environment information. The proposed system is a portable client with a low-power wireless communication method. It is possible to reliably transmit and receive the measured data through a multi-threaded server to monitor the trend of pollutants in the air in real-time.

• Journal of Power Electronics
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• 제16권2호
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• pp.704-716
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• 2016

Small distributed generation units are usually connected to the main electric grid through single-phase voltage source inverters. Grid operating conditions such as voltage and frequency are not constant and can fluctuate within the range values established by international standards. Furthermore, the requirements in terms of power factor correction, total harmonic distortion, and reliability are getting tighter day by day. As a result, the implementation of reliable and efficient control algorithms, which are able to adjust their control parameters in response to changeable grid operating conditions, is essential. This paper investigates the configuration topology and control algorithm of a single-phase inverter with the purpose of achieving high performance in terms of efficiency as well as total harmonic distortion of the output current. Accordingly, a Second Order Generalized Integrator with a suitable Phase Locked Loop (SOGI-PLL) is the basis of the proposed current and voltage regulation. Some practical issues related to the control algorithm are addressed, and a solution for the control architecture is proposed, based on resonant controllers that are continuously tuned on the basis of the actual grid frequency. Further, intentional islanding operation is investigated and a possible procedure for switching from grid-tied to islanding operation and vice-versa is proposed.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권1호
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• pp.126-142
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• 2016

This paper presents a wide-frequency-range, low-power transceiver with an automatic impedance-matching calibration for TV-white-space (TVWS) application. The wide-range automatic impedance matching calibration (AIMC) is proposed for the Drive Amplifier (DA) and LNA. The optimal $S_{22}$ and $S_{11}$ matching capacitances are selected in the DA and LNA, respectively. Also, the Single Pole Double Throw (SPDT) switch is integrated to share the antenna and matching network between the transmitter and receiver, thereby minimizing the systemic cost. An N-path filter is proposed to reject the large interferers in the TVWS frequency band. The current-driven mixer with a 25% duty LO generator is designed to achieve the high-gain and low-noise figures; also, the frequency synthesizer is designed to generate the wide-range LO signals, and it is used to implement the FSK modulation with a programmable loop bandwidth for multi-rate communication. The TVWS transceiver is implemented in $0.13{\mu}m$, 1-poly, 6-metal CMOS technology. The die area of the transceiver is $4mm{\times}3mm$. The power consumption levels of the transmitter and receiver are 64.35 mW and 39.8 mW, respectively, when the output-power level of the transmitter is +10 dBm at a supply voltage of 3.3 V. The phase noise of the PLL output at Band 2 is -128.3 dBc/Hz with a 1 MHz offset.

• 한국통신학회논문지
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• 제34권11C호
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• pp.1098-1105
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• 2009

본 논문에서는 낮은 복잡도와 전력 소모로 정밀한 무선측위 성능을 제공할 수 있는 고속 비동기식 UWB(Ultra Wide band) 무선측위 기법을 제안하고, NLoS (Non-Line of Sight) 특성이 강한 다중경로 채널 환경에서 무선측위 성능을 향상시키기 위한 Residual Test를 적용한다. 비콘 (Beacon) 수만큼의 송수신이 요구되는 일반적인 ToA (Time of Arrival) 무선측위 기법과 비교하여, 제안된 UWB 무선측위 기법은 단일 송수신 과정만 필요하므로 소모 전력 및 처리 시간 등을 효과적으로 감소시킨다. 또한 비콘간의 엄격한 시각 동기화가 요구되는 일반적인 TDoA (Time Difference of Arrival) 무선측위 기법과 비교하면, 비동기식 기반 제안된 기법은 시스템 복잡도가 매우 낮은 특성을 보유하고 있다. LoS (Line of Sight) 채널 모델에서의 모의실험 결과, 제안된 기법은 낮은 시스템 복잡도와 전력 소모 등을 요구하지만 일반적인 ToA 및 TDoA 무선측위 기법들과 거의 동등한 정밀도의 무선측위 성능을 제공하는 것을 확인하였다. 더불어, NLoS 특성이 강한 다중경로 채널 환경에서도 제안된 기법은 Residual Test를 이용하여 일반적인 기법들에 근접한 정밀도의 무선측위 성능을 달성하는 것을 확인하였다.

• 전기학회논문지
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• 제64권3호
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• pp.433-437
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• 2015

We have designed and fabricated a low power and high linearity up down convertor for wireless repeaters using $0.35{\mu}m$ SiGe Bipolar CMOS technology. Repeater is composed of a wideband up/down converting mixer, programmable gain amplifiers (PGA), input buffer, LO buffer, filter driver amplifier and integer-N phase locked loop (PLL). As of the measurement results, OIP3 of the down conversion mixer and up conversion mixer are 32 dBm and 17.8 dBm, respectively. The total dynamic gain range is 31 dB with 1 dB gain step resolution. The adjacent channel leakage ratio (ACLR) is 59.9 dBc. The total power consumption is 240 mA at 3.3 V.

• Smart Structures and Systems
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• 제15권1호
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• pp.15-40
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• 2015

This paper proposes a structural damage identification approach based on the power spectral density transmissibility (PSDT), which is developed to formulate the relationship between two sets of auto-spectral density functions of output responses. The accuracy of response reconstruction with PSDT is investigated and the damage identification in structures is conducted with measured acceleration responses from the damaged state. Numerical studies on a seven-storey plane frame structure are conducted to investigate the performance of the proposed damage identification approach. The initial finite element model of the structure and measured acceleration measurements from the damaged structure are used for the identification with a dynamic response sensitivity-based model updating method. The simulated damages can be identified accurately without and with a 5% noise effect included in the simulated responses. Experimental studies on a steel plane frame structure in the laboratory are performed to further verify the accuracy of response reconstruction with PSDT and validate the proposed damage identification approach. The locations of the introduced damage are detected accurately and the stiffness reductions in the damaged elements are identified close to the true values. The identification results demonstrated the accuracy of response reconstruction as well as the correctness and efficiency of the proposed damage identification approach.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.575-578
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• 2005

We report on a low-cost V-band wireless transceiver with no use of any local oscillator in the receiver block using a self-heterodyne architecture. V-band Microwave monolithic IC (MMIC) modules were developed to demonstrate the wireless transceiver using coplanar waveguide (CPW) and GaAs PHEMT technologies. The MMIC modules such as the MMIC low noise amplifier (LNA), medium power amplifier (MPA) and the up/down-mixer were installed in the transceiver system. To interface the MMIC chips with the component modules for the transceiver system, CPW-to-waveguide fin-line transition modules of WR-15 type were designed and fabricated. The fabricated LNA modules showed a $S_{21}$ gain of 8.4 dB and a noise figure of 5.6 dB at 58 GHz. The MPA modules exhibited a gain of 6.9 dB and a $P_1$ $_{dB}$ of 5.4 dBm at 58 GHz. The conversion losses of the up-mixer and the down-mixer module were 14.3 dB at a LO power of 15 dBm, and 19.7 dB at a LO power of 0 dBm, respectively. From the measurement of V-band wireless transceiver, a conversion gain of 0.2 dB and a P $_{1dB}$ of 5.2 dBm were obtained in the transmitter block. The receiver block showed a conversion gain of 2.1 dB and a P $_{1dB}$ of -18.6 dBm. The wireless transceiver system demonstrated a successful data transfer within a distance of 5 meters.