• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.1035-1040
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• 2009

We propose a new encoder/decoders based on an tune able wavelength converter(TWC) and an arrayed waveguide grating(AWG) router for large capacity optical CDMA networks. The proposed encoder/decoder treats codewords of wavelength/time 2-D code simultaneously using the dynamic code allocation property of the TWC and the cyclic property of the AWG router, and multiple subscribers can share the encoder/decoder in networks. Feasibility of the structure of the proposed encoder/decoder for dynamic code allocation is tested through simulations using two wavelength/time 2-D codes, which are the generalized multi-wavelength prime code(GMWPC) and the generalized multi-wavelength Reed-Solomon code(GMWRSC). Test results show that the proposed encoder/decoder can increase the channel efficiency not only by increasing the number of simultaneous users without any multiple-access interference but by using a relatively short length CDMA codes.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.2
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• pp.94-102
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• 2020

Considering that the output voltage and current of a single PV panel are limited in PV power generation, a PV array should be constructed by connecting several PV panels in series and parallel to meet the required voltage/power levels for power generation capacity. When a PV array is partially shaded, the maximum power generation depends on the configuration of a PV array and the presence or absence of blocking diodes. This study considers six PV array configurations and the presence or absence of blocking diodes. An optimum connection structure was proposed to maximize power generation in a partial shadow condition. Results were verified through simulation and an experiment.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.151-152
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• 2016

최근 저압직류배전에 대한 연구가 급속도로 진행되면서 배전망에 적용되는 구성요소에 대한 연구가 활발히 진행 중이다. 본 논문에서는 대용량 수용가 배전반에 접속된 구성요소 중 배전계통으로부터 직류전력 공급하기 위한 양방향 DC/DC 컨버터, 수용가 직접 전력공급을 위한 직류 저압 태양광 발전시스템용 DC/DC 컨버터, 저압 직류 에너지저장시스템용 DC/DC 컨버터의 운전에 있어서 배전계통간 전력조류를 양방향 운전의 타당성에 대해 비교하고, 운용상 얻어지는 효율 개선 등에 대한 것을 비교 검토하고자 한다.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.180-184
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• 1989

Overviews of vertical and horizontal GaAs/AlGaAs OEIC are shown. Researching double Zn diffusion process, we obtain Xj=At1/2-Bd1, where A=2.5${\mu}{\textrm}{m}$/[hr]1/2, B=0.625, of which process is recommended for exact diffusion interface area control of GaAs/AlGaAs. It is proved to be 100A/100A AlAs/GaAs using MOCVD by measurement of photo-luminescence which shows a luminescence peak corresponding to the 798.4nm wavelength calculated values of 38meV ground state above GaAs conduction band.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.161-166
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• 2021

To prevent accidents caused by changes in the surrounding environment or other factors, various protection facilities are installed at the photovoltaic connection module. The main causes of fire are sparks due to foreign substances inside the photovoltaic connection module through high temperature rise and dew condensation in the photovoltaic connection module, and fire due to heat from the power diode. The proposed method can predict the fire by measuring flame, carbon dioxide, carbon monoxide, temperature, humidity, input voltage, and current on the photovoltaic connection module, and when the fire conditions are reached, fire alarm and power off can be sent to managers and users in real time to prevent fire in advance.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.33-38
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• 2022

A solar power generation system uses a solar module that collects solar radiation energy, a connecting board that collects DC power generated from the solar module, and a diode to prevent reverse current from flowing from an inverter to the solar module. The existing photovoltaic connection module consists of only fuses and diodes for reverse polarity and overcurrent blocking, and does not have fire diagnosis, prevention, and suppression functions in the event of a fire. To solve this problem, this paper presents a method to monitor the internal state of the photovoltaic connection module using several sensors and to prevent and extinguish a fire using solenoid valves and fire extinguishing agents when a fire is detected. Through the experiment, it was confirmed that the proposed method normally suppresses the fire in event of a fire.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1134-1141
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• 1999

In this paper, we implement an optical code division multiple access(OCDMA) system and analyze the performance of the implemented system. In the implemented system, a transmitter encodes input data into optical pulses by using laser diode, and spreads the encoded pulses in an encoder which consists of 4 stage delay lines. The decoder which is the same structure as that of encoder delays and combines the spreaded pulses, and thus recovers the original data. At first, we discuss the auto- and cross-correlations of OCDMA signals under both environments of single user and multi-users, and then verify the simulation results with experimental results. We also evaluate the effect of a number of stages of delay line and code length on the system performance through computer simulations. As experimental results we can see that if the decoder have the same configuration as that of encoder, the peak auto-correlation characteristics can be achieved, and thus we can recover the original data from received data. As simulation results we can see that although bit error rate decreases as code length decreases or the number of stage of delay line increases, it is difficult to implement the system because the pulse width becomes narrow. From the results, we can apply CDMA technologies to optical communication networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.8-15
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• 2006

In this paper, we propose the iterative receiver for LDPC-coded OFDMA systems in uplink environments. Applying the Wiener filtering to pilot symbols, an initial channel estimation can be performed effectively. To reduce the complexity of the Wiener filtering, we approximate Wiener filtering coefficients to pre-determined coefficients according to estimated correlation of channel. After an LDPC decoding process, soft symbol derived by extrinsic information of decoder outputs is used to estimate channel. we also derive the error variance of channel estimation and maximum ratio combined results. Using combined results, the channel correlation is re-estimated. Then the proper Wiener filtering coefficients are chosen according to the re-estimated result of the channel correction. Using a computer simulation, we show that the proposed receiver structure has the better performance than the receiver using only pilot symbols.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.863-870
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• 2003

The digital transmission system entered in a RF region as digital system use IC chips of the speeder edge rate and clock speed nowadays. Optical path really was used in order to obtain the more capacity. In this paper, we described importance of electrical interconnect to get the signal integrity in optical module by simulation and experiment. 12 channel${\times}$2.5 G/ps optical parallel transmitter modules were manufactured by two different method ; access lines with microstrip and stripline type. We have clearly shown that the optical module adopting microstrip type with S$\sub$11/ $\geq$ -10 dB presents distortion but the optical module adopting stripline type with S$\sub$11/ $\leq$ : 15 dB obtains eye opening in 2.5 Gbis optical eye pattern response.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.153-161
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• 2005

In a multi-channel network based of wavelength division multiplexing (WDM) technology, an efficient protocol is needed in order for the transmitter and receiver to be tuned to the same wavelength during message transmission time. This paper proposes a priority-based reservation protocol that can efficiently support variable-length messages that require different QoS requirements. In this proposed protocol, high-priority nodes can reserve the data channel before low-priority nodes. However, once a node reserves a data channel successfully, it can persistently use the reserved channel till message transmission is finished regardless of the priority of the node. Moreover, the protocol can operate independently of the number of nodes, and any new node can join the network anytime without requiring network re-initialization. The protocol is analyzed with a finite population model and the throughput-delay characteristics are investigated as performance measures.