• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.23-31
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• 2015

In this paper, we design a SSD(simultaneous single band duplex) system using RF cancellation and digital cancellation. And then, we analyze performance of the SSD system using pre-distorter with HPA non-linearity. Also, we analyze digital cancellation performance of the SSD system using pre-distorter with HPA non-linearity. Additionally, digital cancellation cancels residual self-interference. In linear conditions, digital cancellation can cancel self-interference of 40dB. Therefore, the SSD system has good BER performance because most of self-interference is canceled. But, in HPA non-linearity conditions, digital cancellation cancels residual self-interference of 25dB. In this conditions, self-interference is greater than desired signal. Therefore, bit informations of distant station can not be received. But, we confirm that if the proposed system uses pre-distorter then bit information of distant station can be received by HPA non-linearity compensation. Also, we confirm that even though the proposed system uses pre-distorter, if HPA non-linearity increases then digital cancellation performance is degraded by imperfect compensation of HPA non-linerity.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.472-481
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• 2002

In this paper, the instantaneous flux Is applied to control the position of the SRG (Switched Reluctance Generator) without position sensor. The position information of the rotor is required in the drive of SRG. These data are generally obtained by a shaft encoder or resolver. In some cases, the EMI(Electro Magnetic Interference), vibration, thermal, and humidity environments may cause the difficulties in maintaining the satisfactory performance for the position detection. Therefore, the elimination of the position and speed sensor is needed. In this paper, a new method for the position estimation of the SRG is proposed. The estimation of the flux is calculated by using the measured voltage and current. The rotor position gets from the flux profile. The output voltage is also controlled constantly by PR control algorithm. These methods are verified by computer simulations md experiments using DSP. Experimental results certificate that the proposed method is able to control the SRG stable, and keep the output voltage constant in spite of changing of the load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.294-301
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• 2000

One of the most important design parameters in a microwave radio transmitting system is to reduce spurious response from the output spectrum of the transmitting system. A Local oscillator (LO) is seldom totally pure and at the least contain some LO harmonic signals. A LO or any oscillator is a transmitter if provided with a suitable radiator, conduction, or leakage path. Where mixer is employed in the output of the LO mixer generated spurs can be increased by RF amplifier. To reduce LO leakage, notch filter or band pass filter has been conventionally used. In this paper, the leakage reduction(LR) signal, which has the same magnitude and the opposite phase with respect to LO leakage signal, is added to the output of mixer of the wireless LAN system. The LO leakage is reduced by 30 dB more than the conventional methods do. The proposed method is potentially suitable for low-cost, reliable, and simple application of monolithic microwave integrated circuits (MMICs)

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.1
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• pp.19-25
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• 1999

To achieve high efficiency in high power and high frequency applications, reduction of switching losses and noise is very important. In this paper, an improved zero voltage switching forward dc/dc converter is proposed. The proposed converter is constructed by using energy recovery snubbers in parallel with the main switches and output diodes of the conventional forward dc/dc converter. Due to the use of the energy recovery snubbers in the primary and secondary side, the proposed converter achieves zero-voltage-switching turn-off without switching losses for switching devices and output rectification diodes. The complete operating principles and experimental results will be presented.

• Journal of Power Electronics
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• v.14 no.2
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• pp.203-216
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• 2014

In the conventional dc-dc converter, a pair of additional diode and the adjacent passive component capacitor/inductor can be added to the circuit with an X-shape connection, which generates a family of new topologies. The novel circuits, also called diode-assisted dc-dc converter, enhance the voltage boost/buck capability and have a great potential for high step-up/step-down power conversions. This paper mainly investigates and compares conventional dc-dc converter and diode-assisted dc-dc converter in wide range power conversion from the aspects of silicon devices, passive components requirements, electro-magnetic interference (EMI) and efficiency. Then, a comprehensive comparison example of a high step-up power conversion system was carried out. The two kinds of boost dc-dc converters operate under the same operation conditions. Mathematical analysis and experiment results verify that diode-assisted dc-dc converters are very promising for simultaneous high efficiency and high step-up/step-down power conversion in distributed power supply systems.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1821-1834
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• 2017

Medium voltage control applications due to obtain better output voltage and reduced electro-magnetic interference multi level inverter is used. In closed loop control with inverter, the PI controller does not operate satisfactorily when the operating point changes. This paper presents the performance of Co-Efficient diagram PI controller based indirect vector controlled induction motor drive fed from three-level inverter under different operating conditions (dynamic and steady state). The proposed Co-Efficient diagram PI controller based three level inverter significantly reduces the torque ripple compared to that of conventional PI controller. The performance of the indirect vector controlled induction motor drive has been simulated at different operating conditions. For three-level inverter control, a simplified space vector modulation technique is implemented, which reduces the coordinate transformations complications in the algorithms. The performance parameters, torque ripple contents and THD of induction motor drive with three-level inverter is compared under different operating conditions using CDM-PI and conventional PI controllers.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.2
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• pp.67-78
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• 1994

1996년부터 유럽연합을 중심으로 전자파내성(Electromagnetic immunity; 흔히 군사규격에서는 전자파감응성(electromagnetic susceptibility)이라 함) 규제가 본격적으로 시작될 전망이다. 이러한 전자 파내성 규제는 우리가 과거 '80년대 초에 경험했던 전자파방출(electromagnetic emission; 흔히 electro- magnetic interference 라고도 표현한다) 규제에 비해 규제주파수가 대폭 확장됨(9KHz - 1GHz .rarw. 50/60 Hz - 40 GHz)은 물론, 규제항목도 크게 늘어나기(2개 항목 .rarw. 11개 항목)때문에 본격 규제가 시작되면 우리 산업체에 큰 피해를 초래할 것으로 우려된다. 특히 "복사 전자기장에 대한 전자파내성 요구사항"은 일부 전자파내성 측정항목을 포함하고 있던 안전규 격 등에서도 다루고 있지 않던 것으로서 우리에게는 매우 생소한 항목이다. 이 항목은 과거 미국의 군사 규격등에서 요구했던 항목인데, 앞으로 각국의 상용규격에도 대폭 추가될 것으로 보인다. 이러한 규제는 우리의 생활환경에서 결코 빼놓고 생각할 수 없는, 동시에 가장 큰 전자파장해원인 의도적 복사로서의 방 송신호 및 각종 무선통신 신호에 대해 전기, 전자기기가 전자파내성을 갖고, 성능저하나 오동작을 유발하 지 않아야 함을 요구하는 것이다. 이러한 항목의 평가를 위해서는 대형 시험환경(EMS chamber)과 표준 전자기장 발생장치(signal genera- tors + high power amplifiers), 그리고 오동작 모니터링 장치(monitorring equipments) 등이 필요하기 때 문에 평가시스템 구성에 막대한 비용이 소요된다. 따라서 시스템 구성에 매우 신중을 기해야 하며, 관련 국제표준화규격을 사전에 철저히 이해하여 관련 시험검사를 위한 투자계획을 수립하는 것이 바람직하다. 본 고에서는 복사 전자기장에 대한 대표적인 국제표준화규격을 소개하고, 나아가서 그러한 항목의 평가 시스템의 설계 및 구현에 대해서 설명할 것이다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.677-684
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• 2018

In this paper, we propose a method for high-frequency modeling of transformers using the S-parameter. The open and short circuits of the primary and secondary sides were configured, and the reflection coefficient in each circuit was measured using a vector network analyzer. The equivalent circuit elements were extracted from the measured results to model the high-frequency equivalent circuit, and the validity of the method was verified by comparing the measured S-parameters in a 2-port network with the simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.761-765
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• 2008

This study presents an effective methodology on integrated monitoring system for a maglev guideway using WDM-based FBG sensors. The measuring quantities include both local and global quantities of the guideway response, such as stains, curvatures, and vertical deflections. The strains are directly measured from multiplexed FBG sensors at various locations of the test bridge followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the Bernoulli beam theory and regression analysis. Frequency contents obtained from the proposed method are compared with those from a conventional accelerometer. Verification tests were conducted on the newly-developed Korean Maglev test track. It has been shown that good agreement between the measured deflection and the estimated deflection is achieved. The difference between the two peak displacements was only 3.5% in maximum and the correlations between data from two sensing systems are overall very good. This confirms that the proposed technique is capable of tracing the dynamic behavior of the maglev guideway with an acceptable accuracy. Furthermore, it is expected that the proposed scheme provides an effective tool for monitoring the behavior of the maglev guideway structures without electro magnetic interference.

• Journal of Korea Multimedia Society
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• v.18 no.3
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• pp.401-407
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• 2015

In this paper, we propose the method to eliminate EMI (Electro-Magnetic Interference) in ELF (Extremely Low Frequency) band below 2 KHz for extending the gesture-recognition distance of smart TVs to more than 3m using electric potential sensor. First, we measure the electric field generated from the back panel of a TV and propose the effective arrangement of two sets of differential sensors as well as the shielding method using metal fiber. Also, we eliminate the PLN (Power Line Noise) and other noise generated from the TV and sensors as well as surrounding environments using filters. Using the proposed EMI eliminating methods, we evaluate displacement ratio on measured signals according to distance between sensors and a moving hand. Experiment results show that our proposed method can extend the hand-gesture sensing distance using EPS (Electric Potential Sensor) up to more than 3m, which is enough to satisfy applicability of EPS based remote control to Smart TVs.