• 대한전자공학회논문지SP
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• 제47권5호
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• pp.117-126
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• 2010

산란선을 흡수하여 보다 선명한 x선 영상을 얻기 위하여 산란방지 그리드를 사용하여 투사영상을 얻는데, 이때 그리드로 인한 왜곡이 발생한다. 본 논문에서는 회전된 그리드를 사용하여 투사영상을 얻고 단순한 1차원 저역필터를 영상의 공간영역에서 각 축으로 별도로 적용하여 그리드 왜곡을 효율적으로 제거하는 방법을 제안하고 그 성능을 고찰해 보았다. 제안한 방법은 왜곡 주파수를 별도로 예측할 필요 없이, 회전된 그리드를 사용하여 획득한 영상에 단순한 1차원 필터를 주파수영역이 아닌 공간영역에서 적용하므로 매우 단순하여 쉽게 구현이 가능하며 빠른 계산 속도를 가지는 장점을 가지고 있으면서 그 성능은 주파수영역에서 2차원 필터를 적용한 경우와 유사하다.

• 한국전자파학회논문지
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• 제15권7호
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• pp.706-712
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• 2004

본 논문에서는 Ka대역 위성 중계기용 출력 멀티플렉서의 설계 및 제작에 대하여 언급하였다. 출력 멀티플렉서는 저역통과필터, 채널필터, 매니폴드(Manifold)로 구성되어 있으며, 위성 중계기의 무게와 부피를 최소화하기 위하여 채널필터는 이중모드로 설계하였다. 채널별 주파수 선택도를 높이기 위하여 채널필터는 4차 타원 응답형으로 설계하였으며, 저역통과 필터는 13차 corrugated 형으로 설계하였다. 채널필터와 매니폴드의 초기 설계 후 최적화 과정에 있어서 모든 설계 변수를 최적화시키는 대신 일부의 설계 변수만을 최적화시킴으로써 용이하게 최적화 설계할 수 있음을 확인하였다. 제작한 Ka 대역 위성 중계기용 출력 멀티플렉서의 측정결과는 설계결과와 동일한 특성을 나타내었다.

• Progress in Superconductivity
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• 제4권2호
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• pp.132-136
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• 2003

Extremely selective high temperature superconducting (HTS) band -pass filters were developed for the base transceiver station applications of Digital Cellular communication Service (DCS). The filters have a bandwidth of 25 MHz at a center frequency of 834 MHz. There are 12 resonators which have spiral-meander microstrip-line structures in order to reduce far-field radiations with a reasonable tunability. As a result, the size of filters is 5 mm $\times$ 17 mm $\times$ 41 mm. Device characteristics exhibited a low insertion loss of -0.4 dB with a -0.2 dB ripple and a return loss better than -10 dB in the pass-band at 65 K. The out-of-band signals were attenuated better than 60 dB about 3.5 MHz from the lower band edge, and 3.8 MHz from the higher band edge.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.389-392
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• 1996

The recent development of high temperature superconducting epitaxial thin film offer great potential for planar passive microwave application such as ring resonator, filters, transmission lines, and antennas. This paper describes the fundamental properties of Microstrip Band-Pass Filter using HTS Thin Film and its application to microwave devices. In order to fabricate HTS microstrip multiple filters, We have grown laser ablated HTS thin films, patterned by photolithographic process and wet etching processes intro HTS microwave devices.

• Journal of Power Electronics
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• 제18권1호
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• pp.160-170
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• 2018

For high power photovoltaic (PV) grid-connected converters, high order filters such as multi-tuned filters and Traps+RC filters with outstanding filtering performance have been widely researched. In this paper, the optimization of a multi-tuned filter with a low damping resistance and research on its corresponding control scheme have been combined to improve the performance of the proposed filter. Based on the characteristics of the switching harmonics produced by PWM, the proposed filter is optimized to further improve its filtering performance. When compared with the more common Traps+RC filter, the advantages of the proposed filter with low damping resistances in attenuating the major switching harmonics have been demonstrated. In addition, a simpler topology and reduced power loss can be achieved. On the other hand, to make the implementation of the proposed filter possible, on the base of the unique frequency response characteristic of the proposed filter, a digital single-loop control scheme has been proposed. This scheme is a simple and effective means to suppress the resonance peak caused by a lack of damping. Therefore, a smaller volume, better efficiency of the proposed filter, and easy implementation of the corresponding control scheme can be realized. Finally, the superiority of the proposed filter topology and control scheme is verified in experiments.

• Journal of Power Electronics
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• 제19권1호
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• pp.44-57
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• 2019

Recently, the use of LLCL filters for grid inverters has been suggested to give better harmonic attenuation than the commonly used L and LCL filters, particularly around the switching frequency. Nevertheless, this filter is mainly designed for constant switching frequency pulse width modulation (CSF PWM) methods. In variable switching frequency PWM (VSF PWM), the harmonic components are distributed across a wide frequency band which complicates the use of a high order filter, including LCL and LLCL filters. Recently, a confined band variable switching frequency (CB-VSF) PWM method has been proposed and demonstrated to be superior to the conventional constant switching frequency (CSF) PWM in terms of switching losses. However, the applicability of LLCL filters for this type of CB-VSF PWM has not been discussed. In this paper, the authors study the suitability of an LLCL filter for CB-VSF PWM and propose design guidelines for the filter parameters. Using simulation and experimental results, it is demonstrated that the effectiveness of an LLCL filter with CB-VSF PWM depends on the parameters of the filters as well as the designed variable frequency band of the PWM. Simulation results confirm the performance of the suggested LLCL design, which is further validated using a lab scale prototype.

• 한국통신학회논문지
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• 제22권4호
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• pp.637-637
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• 1997

본 논문에서는 MPEG-4 비데오 VB(verification model)에서 입력 영상의 크기 변환을 위하여 제시한 포멧 변화필터보다 하드웨어 구현시 더 유리한 필터를 제안한다. 제안된 필터는 각 계수가 MSD(minimal signed digit)로 표현되었을 때 0이 아닌 자리수가 두 개 이하가 되도록 설계하였으며 입력과 필터 계수와의 곱을 하나의 덧셈기만으로 구현할 수 있어서 일반적인 필터에서와 같이 정수 곱셈기나 CSA(carry save adder)를 사용하는 경우보다 복잡도나 속도 면에서 더 유리하다. MPEG 비데오 VM에서 제시한 필터는 2:1, 4:1, 5:3, 5:6 변화 등 모두 여섯가지인데 이들 중 매우 간단한 필터 하나를 제외한 나머지 필터에 대하여 모두 각 계수가 0이 아닌 자리수가 두개 이하가 되도록 설계를 하고 이들을 MPEG에서 제시한 필터들과 비교하였다. 필터링 성능 비교 방법은 사인파를 입력으로 하여 출력과 참값을 비교하는 간접적인 방법과, 영상을 높은 정밀도 계산으로 높은 탭수의 필터를 통과시켜 얻은 결과를 원영상으로 하여 제안된 필터와 MPEG에서 제시된 필터를 통과한 영상들을 PSNR로 비교하는 방법을 사용하였다. 결국, 본 논문에서 제시된 포맷 변환 필터들은 하드웨어 구현이 매우 간단하고 속도가 빠르면서도 필터링된 영상의 화질 면에서는 MPEG에서 제시한 필터와 거의 같음을 알 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1852-1854
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• 1999

In order to enhance satellite communication system performance, filters are required with the characteristics of sharp skirt, low insertion loss, and high power handling capability. But the performance of microwave passive filters is significantly declined by the conduction losses, especially in case of planar structures using film conductors. By using high temperature superconducting(HTS) film material as the conductor, higher performance could be expected. We have designed and developed narrow bandpass filters using haripin-type superconducting microstrip line for satellite communication. High quality superconducting YBCO thin films have been grown on MgO substrates by pulsed laser deposition(PLD) The deposited YBCO films were patterned by conventional wet-etching process. The transition temperatures of these films had shown 86 - 89 K. The film thicknesses were about 500 nm. Experimental results are presented for the insertion loss and return loss of the filter at 60 K.

• International Journal of Ocean System Engineering
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• 제1권4호
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• pp.205-210
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• 2011

High data-rate underwater communications is demanded. This demand imposes stringent requirements on underwater communication equipment of phase-locked-loop (PLL). Phase noise in PLL is unwanted and unavoidable. In this paper, we investigate the PLL phase noise effect on high order QAM for underwater communication systems. The phase noise model using power spectral density is adopted for performance evaluation. The phase noise components considered in PLL are reference oscillator, voltage controlled oscillator (VCO), filter and divider. The filters in PLL noise are assumed to be second order active and passive low pass filters. Through simulation, we analyze the phase noise characteristics of the four components and then investigate the performance improvement factor of each component. Consequently, we derive specifications of VCO, phase detector, divider to meet performance requirement of high data-rate communication using QAM under phase noise influence.

• Journal of Power Electronics
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• 제13권2호
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• pp.287-295
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• 2013

The use of LCL filters in pulse width modulation voltage source converters is a standard solution for providing proper attenuation of high-order grid-current harmonics. However, these filters can cause the undesired effect of resonance. This paper proposes an active damping strategy with harmonics compensation. It can alleviate the harmonics around the resonance frequency caused by the LCL filters. The proposed strategy is attractive since it is simple, does not depend on grid parameters and does not increase the number of sensors. Simulation and experimental results verify the effectiveness of the proposed active damping strategy.