• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.469-479
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• 2009

The GEM frame is used a mean to deliver the variable length user data and consists of the header and the payload in the G-PON system. The HEC field of header protects contents of the header and is used to maintain GEM frame synchronization at the same time. When an LCDG (Loss of GEM Channel Delineation) occurs while receiving frames, the receiver have to discard corrupted frames until acquiring the synchronization again. Accordingly, high-speed synchronization method is required to minimize the frame loss. In this paper, we suggest not only a main state machine but a sub-state machine to reduce the frame loss when undetectable errors occurred in the GEM header. Also, we provide a more efficient and fast parallel structure to detect the starting point of the header. Finally, the proposed method is implemented with the FPGA and verified by the logic analyzer.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.283-284
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• 2016

산업계에 널리 쓰이고 있는 회전자 자속기준 벡터제어(FOC)와 달리 직접토크제어(DTC)는 고정자 자속기준으로 토크와 자속을 직접 제어한다. 토크는 전류센서를 이용하여 검출한 고정자 전류와 고정자 자속을 곱하여 구한다. 고정자 자속은 매우 빠르게 스위칭되는 전압벡터지령을 이용하여 얻게 되므로, 고정자 자속각을 이용한 속도추정에 어려움이 있다. 따라서, 본 논문은 관측기를 이용한 직접토크제어의 속도 센서리스 구현기법을 제안하고, 기존의 속도추정 기법과 제안하는 기법을 시뮬레이션을 통해 비교한다.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.90-93
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• 2007

본 연구에서는 전압품질에 민감한 설비를 위한 3상 하이브리드 Z-소스 동적 전압 보상기(Z-HDVR : Hybrid Z-Source Dynamic Voltage Restorer)을 제시하였다. 제안된 시스템은 수동필터와 Z-소스 토폴로지의 직렬형 능동필터로 구성된다. Z-HDVR의 ESS(Energy Storage System)로는 친환경적인 고분자 전해질 연료전지(PEMFC : Proton Exchange Membrane Fuel Cells)를 사용하였다. 고조파 검출 알고리즘은 동기좌표계의 $i_d-i_q$ 이론에 의하였으며, 부하전압 보상을 위하여 PI제어를 사용하였다. 전압swell 및 sag등 다양한 전원 조건하에서 제안된 시스템의 보상 성능을 검토하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.671-678
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• 2014

This paper presents a Ka-band FMCW sensor that has high linearity by improving a nonlinear behavior of the voltage controlled oscillator. Due to the nonlinear characteristics of the voltage controlled oscillator for the conventional method, the drift of beat frequency can cause inaccuracy and errors to the extracted results. A Ka-band FMCW signal with fast transition time could be generated by using both direct digital synthesizer and phase locked loop in this research. The implemented FMCW sensor showed very high accuracy in beat frequency through the test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.952-960
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• 2004

PSK(Phase Shift Keying) is useful because of the power and spectral efficient modulation. In this paper, no additional hardware will be needed to support various transmit mode in the suggested DSP scheme. We design and implement the synchronization algorithm for M-ary PSK(M=2, 4) demodulator based on DSP scheme, instead of complex analog PSK demodulator. TMS320C6203 is used as DSP. We check the all kinds of waveforms via the graph view window after software programming the emulation on the DSP tool. The result of implementation proves that demodulator using the suggested algorithm has equal performance with demodulator using analog circuits.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.4
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• pp.286-294
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• 2011

Cable modems typically are implemented by a forward error correction(FEC) scheme. The ITU-T Recommendation J-38 Annex B specifies using 64- and 256- quadrature amplitude modulation (QAM) and extended RS coding scheme. In implementing the cable modem, there are some problems to fabricate and fitting on FPGA chip. First, many clocks are needed in implementing cable modem because of different code rate and different modulation types. To reduce the number of clocks, we use the two memories, which are different clock speed for reading and writing data. Second, this system lost the bit-synchronization and frame-synchronization in decoder, the system recognize that all data is error. This paper solves the problems by using simple 5-stage registers and unique sync-word. Based on solutions for about problems, the cable modem is fabricated on FPGA chip name as Vertex II pro xc2vp30-5 by Xilinx, and we confirmed the effectiveness of the results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.22-28
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• 2002

A protection scheme for Unified Power Quality Conditioner (UPQC) is presented and analyzed in this paper. The proposed UPQC has the series active power filter operated as a high impedance k($\Omega$) to the fundamentals when the over current occurs in the power distribution system, and three control strategies are proposed in this paper. The first is the method by detecting the fundamental source current through the p-q theory,［1］ the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF) and the third is the method by detecting the input voltage. When the over current occurs in the power distribution system, the proposed scheme protects the UPQC without additional protection circuits. The validity of proposed protection scheme is investigated through simulation results.

• Journal of IKEEE
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• v.22 no.2
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• pp.432-439
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• 2018

In this paper, an omnidirectional visible light detector was developed by making the detecting surface of a flexible solar cell in a cylindrical form, which has a uniform receiving pattern in the horizontal plane. This solar cell detector receives simultaneously multiple signal lights incident from different directions and provides electrical power to the ASK demodulator in the receiver. In experiments, time division transmission method was used to receive three signal lights incident from different directions to the solar cell detector. Each signal light was ASK modulated using a carrier of 40 kHz, and the synchronizing pulses required for time division transmission were generated by detecting the 120 Hz AC signal included in the indoor illumination lamp with Cds cells. This receiving structure is useful in constructing an $N{\times}1$ optical link in visible light communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1342-1350
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• 1999

In this paper, we have developed and analyzed the 2.45GHz microwave RFID system. Which is composed tag and interrogator using custom IC, and we have made the software driving the hardware for the bidirectional data transmission method. Using 3.6V power supply was used, the optimal identification range in the information transmission of the designed microwave RFID system operating at 9,600bps was l0m. In the control circuit of the tag, the low current consumption of 15$mutextrm{A}$ and the tag data transmission rate of 90% when the moving velocity was 80km/h.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.626-633
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• 2009

ISO/IEC/WD 24753 defines new modem specifications for a long-range RFID communications and application protocol for a sensor tag system. According to the standard, the frequency offset of the tag is 4%. In general wireless communications systems, it is known that a coherent receiver is superior to a non-coherent receiver. However, if the frequency offset is large, it is difficult to restore the original data accurately with a coherent receiver, and the performance of a coherent receiver is easily degraded. In this paper, a non-coherent receiver structure is adopted to solve the frequency offset problem of long-range RFID communications. We designed a frequency estimation block to find an optimal frequency from the received signal with 4% frequency offset and proposed a start frame delimiter (SFD) detection algorithm to determine the start position of the payload. The frequency estimation block finds the optimal frequency from the received signal using 9-correlators. And the SFD detection block searches the received signal to find the start position of the payload with dual correlator. We implemented a long-range RFID reader with the proposed methods and evaluated its performance in a wired/wireless test network. The implemented long-range RFID reader showed more superior performance than the commercial RFID reader in terms of recognition range.