• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.1
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• pp.22-28
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• 2009

This paper presents a fast received signal strength indicator (RSSI) circuit for wireless communication application. The proposed circuit is developed using power detectors and an analog-to-digital converter to achieve a fast settling time. The power detector is consisted of a novel logarithmic variable gain amplifier (VGA), a peak detector, and a comparator in a closed loop. The VGA achieved a wide logarithmic gain range in a closed loop form for stable operation. For the peak detector, a fast settling time and small ripple are obtained using the orthogonal characteristics of quadrature signals. In $0.18-{\mu}m$ CMOS process, the RSSI value settles down in $20{\mu}s$ with power consumption of 20 mW, and the maximum ripple of the RSSI is 30 mV. The proposed RSSI circuit is fabricated with a personal handy-phone system transceiver. The active area is $0.8{\times}0.2\;mm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.104-109
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• 2014

To operate organic light emitting device (OLED) with alternating current (AC) power source without AC/DC(direct current) converter, we fabricated the fluorescent OLED and measured the emission characteristics with AC and DC. The OLED operated by AC showed higher maximum current efficiency of 8.2 cd/A and maximum power efficiency of 8.3 lm/W. But current efficiency and power efficiency of AC driven OLED showed worse than DC driven OLED at high voltage above 10 V. This result can be explained by the peak voltage of AC was $\sqrt{2}$ times than DC, In case of low driving voltage the emission characteristics were improved by the peak voltage of AC, but in case of high driving voltage the emission efficiencies were decreased by the roll off phenomena. Finally, serial OLED arrays using twelve OLEDs driven by AC 110 V showed average voltage of 9.17 V, voltage uniformity of 99.0%, average luminance of $1,175cd/m^2$, luminance uniformity of 94.4%.

• Current Optics and Photonics
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• v.4 no.6
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• pp.472-476
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• 2020

We have investigated the impact of optical filter bandwidth on the performance of all-optical automatic gain-controlled (AGC) erbium-doped fiber amplifiers (EDFAs). In principle, an optical bandpass filter (OBPF) should be placed within the feedback gain-clamping loop to set the lasing wavelength as well as the passband of the feedback amplified spontaneous emission (ASE) in all-optical AGC EDFA. From our measurement results, we found that the power level of feedback ASE with 0.1 nm passband of the optical filter was smaller than the ones with >0.2 nm passband cases. Therefore, the peak-to-peak power variation of the surviving channel with 0.1 nm passband was much larger than the ones with >0.2 nm passband. In addition, no significant difference in the power level of the feedback ASE was observed when the passband of the optical filter was ranging from 0.2 nm to 4.5 nm in our measurements. From these results, we have concluded that the passband of the optical filter should be slightly larger than 0.2 nm by taking into account the effect of feedback ASE power and the efficient use of the EDFA gain spectrum for the lasing ASE peak.

• ETRI Journal
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• v.46 no.2
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• pp.227-237
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• 2024

This study proposes a novel, conditionally applied neural network technique to reduce the overall peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system while maintaining an acceptable bit error rate (BER) level. The main purpose of the proposed scheme is to adjust only those subcarriers whose peaks exceed a given threshold. In this respect, the developed C-ANN algorithm suppresses only the peaks of the targeted subcarriers by slightly shifting the locations of their corresponding frequency samples without affecting their phase orientations. In turn, this achieves a reasonable system performance by sustaining a tolerable BER. For practical reasons and to cover a wide range of application scenarios, the threshold for the subcarrier peaks was chosen to be proportional to the saturation level of the nonlinear power amplifier used to pass the generated OFDM blocks. Consequently, the optimal values of the factor controlling the peak threshold were obtained that satisfy both reasonable PAPR reduction and acceptable BER levels. Furthermore, the proposed system does not require a recovery process at the receiver, thus making the computational process less complex. The simulation results show that the proposed system model performed satisfactorily, attaining both low PAPR and BER for specific application settings using comparatively fewer computations.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.475-483
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• 2000

This paper describes designs about the power system of KITSAT-4 satellite. The KITSAT-4 power system is mainly composed of power stage and control stage. The power stage is a 200〔W〕 buck converter and control stages are hardware controller and software controller The hardware controller is PPT(Peak Power Tracker), battery voltage controller and software controller is battery current controller and direct duty controller. So the operation of power system has many advantages in that it can select controller according to reliable control and precise control. The controller design methods are presented and the small signal analyses are performed to verify system stability.

• ETRI Journal
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• v.29 no.3
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• pp.402-404
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• 2007

One of the major disadvantages of the orthogonal frequency division multiplexing system is high peak-to-average power ratio (PAPR). Selected mapping (SLM) is an efficient distortionless PAPR reduction scheme which selects the minimum PAPR sequence from a group of independent phase rotated sequences. However, the SLM requires explicit side information and a large number of IFFT operations. In this letter we investigate a novel PAPR reduction method based on the radial basis function network and SLM.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.63-66
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• 1998

MC-CDMA(Multi-Carrier Code Division Multiple Access) 시스템에서 전송 신호의 피크 전력 대 평균 전력(Peak-to-Average Power: PAP)율을 낮추는 방안을 제시한다. 확산 코드에 의해 결정된 각 부 캐리어의 위상 오프셋은 전송 신호의 복소 포락선 형성에 영향을 주게 되어 전송 신호의 PAP 율을 결정하게 된다. 따라서 각 부 캐리어의 위상 오프셋을 적절히 조정함으로써 PAP율을 낮출수 있다. 본 논문에서는 PAP 율을 감소시키는 부 캐리어 위상 오프셋 코드의 한 예를 제시하며, 모의 실험을 통하여 전송신호의 크기 분포 특성과 PAP 율의 감소를 확인한다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.421-425
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• 2005

A distributed FBG temperature sensor system was constructed for the use in protection of electric power system. A F-P wavelength tunable filter is used converting temperature-induced wavelength variations to temporal peak locations. We used Gaussian line-fitted algorithm to alleviate the error caused by quantization and electrical noises. The experimental results showed much better accuracy than the raw peak-detection scheme.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.6
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• pp.358-363
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• 2004

Due to the weather sensitivity of the power load, it is difficult to forecast accurately the peak power load of summer season. We improve the accuracy of the load forecasting considering weather condition. We introduced the sensitivity of temperature and proposed an improved forecasting algorithm. The proposed algorithm shows that the error of the load forecasting is 1.5%.