• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.69-76
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• 2005

In this paper, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TM_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of If modes. The size and location of intercavity slot is determined by the coupling equation from E-and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11C
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• pp.1098-1110
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• 2003

In this paper, we propose a homomorphic wavelet-based MMSE filter with edge detection to restore images degraded by speckle noise. In the proposed method, a noisy image is first transformed into logarithmic domain. Each pixel in the transformed image is then classified into flat and edge regions by applying DIP operator to the image restored by homomorphic directional MMSE filter. Each pixel in flat region is restored by homomorphic wavelet-based MMSE filter. Each pixel in edge region is restored by the weighted sum of the output of homomorphic wavelet-based MMSE filtering and that of homomorphic directional MMSE filtering. The restored image in spatial domain is finally obtained by applying the exponential function to the restored image in logarithmic domain. Experimental results show that the restored images by the proposed method have ISNR improvement of 3.3-4.0 ㏈ and ${\beta}$, a measurement parameter on edge preservation, improvement of 0.0103-0.0126 and superior subjective image quality over those by conventional methods.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.4
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• pp.289-293
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• 2009

In sensor networks, many methods have been proposed to process in-network aggregation effectively. Contrary to normal aggregation queries, skyline query processing that compare multi-dimension data for producing result is very hard. It is important to filter unnecessary data for energy-efficient skyline query processing. Existing approach like MFTAC restricts unnecessary data transitions by deploying filters to whole sensors. However, network lifetime is reduced by energy consumption for filters transmission. In this paper, we propose a lazy filtering-based skyline query processing algorithm of in-network for reducing energy consumption by filters transmission. The proposed algorithm creates the skyline filter table (SFT) in the data gathering process which sends from sensor nodes to the base station and filters out unnecessary transmissions using it. The experimental results show that the proposed algorithm reduces false positive by 53% and improves network lifetime by 44% on average over MFTAC.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.431-438
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• 2001

Oxygen saturation of blood is defined as ratio of total hemoglobins density to oxyhemoglobins density And the accuracy of pulse oxymeter that measures the oxygen saturation of blood by a noninvasive method is influenced by a measuring environment, breathing and motion of patient. Especially when patient moved his arms and fingers, it is difficult to eliminate motion artifact because the motion artifact signal has features that are overlap or closed at normal signal in frequency domain. We propose the filtering method that construct the filter banks and a matched falter to improve the Problem. When experimented by the proposed method, the ratio regulation of the proposed methods has 4.1% below than an adaptive filter (39.7%) and a moving average filter (11.2%). So. the Proposed method will be able to get a stable ratio of SpO2.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.779-781
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• 2013

As the demand for various multimedia service increases the technology that utilizes image as information transfer method develops rapidly. Though average filter, median filter and weight filter etc. have been proposed to remove various noises that are added to images, the existing methods are short of noise removal and edge reservation performance. Therefore, in this paper an algorithm, in which noise is decided at the first hand, and then it is processed through modified median filter and adaptive weighted average filter, is proposed to effectively remove the complex noise that has been added to an image. And it was compared with existing methods through simulation and PSNR(peak signal to noise ratio) has been used as a criterion.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.217-219
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• 2019

In response to the increased use of digital video device, more researches are actively made on the image processing technologies. Image processing is practically used on various applied fields such as medical photographic interpretation, and object recognition. The types of image noise include Gaussian Noise, Impulse Noise, and Salt and Pepper. Noise refers to the unnecessary information which damages the video and the noise is mainly removed by a filter. Typical noise removal methods are Median Filter and Average Filter. While Median Filter is effective for removing Salt and Pepper noise, the noise removal performance is relatively lower in the environment with high noise density. To address such issue, this study suggested an algorithm which utilizes neighboring pixels to remove noise.

• The Journal of the Acoustical Society of Korea
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• v.17 no.5
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• pp.57-62
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• 1998

본 논문에서는 입력신호의 시변특성에 따라 분석 필터의 대역을 가변 시키는 필터 뱅크의 구조를 제안한다. 제안된 필터뱅크는 일반적으로 32개의 균일한 대역으로 나누어 임 계대역의 표현을 적절히 표현하지 못하는 Polyphase 필터의 단점을 극복하면서 시스템 설 계에 높은 계산량을 요구하는 QMF-tree 필터의 단점을 보완한다. 본 연구에서는 분할 대역 은 4개에서 26개의 대역으로 가변하고, 웨이블릿 필터중 Daubechies필터를 사용하였다. 제 안된 구조의 부호화기는 128kbps에서 MPEG-a오디오와 비슷한 수준의 CD 음질을 유지하 며, 연산량 비교결과는 PolyPhase filter를 이용한 MPEG보다 부호화, 복호화 과정을 합쳐 다양한 전송률과 음원에서 평균 19%의 감소를 얻었다.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.2
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• pp.145-151
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• 2010

This paper proposes a reverse filtering system of sound field obtaining a state of sound field transmitted from two sounds, using an adaptive filter and neural network. The proposed system uses the reverse filtering method with calculating and renewing a coefficient of a filter, using least mean square. Based on training the neural network, experiments confirm that the proposed system is effective for a simple waveform with non-linear distortion, by using neural network and adaptive filtering method.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.517-517
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• 2015

레이더에 수신된 신호는 신호처리기를 통해 자료의 해석시 불필요한 지형에코를 제거하는 과정을 거친다. 신호처리기의 필터는 레이더의 기종에 따라 다르나, 일반적으로 도플러 속도나 스펙트럼 폭의 값에 따라 지형에코를 제거하며, 이 값들에 따라 번호를 부여하여 필터를 선택적으로 이용할 수 있도록 되어 있다. 본 연구에서는 국토교통부에서 운영하고 있는 비슬산 강우레이더와 소백산 강우레이더의 필터번호에 따른 반사도의 빈도 영역 그래프, 반사도-차등반사도의 빈도 산포도, 반사도와 차등반사도의 평균 및 표준편차를 통해 적정 필터를 선정하고자 하였다. 이 때, 지형에코와 기상에코의 제거 정도 확인을 위해 레이더 관측반경 50 km를 기준으로 비교를 수행하였다. 그 결과, 1번 필터 이후에는 필터에 따른 큰 변화가 없어 1번 필터를 사용하는 것이 기상에코를 보존하면서 지형에코를 제거하는 효과가 가장 좋은 것으로 판단되었다.

• Journal of Digital Convergence
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• v.10 no.10
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• pp.277-282
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• 2012

The speech recognition system can not quickly adapt to varied environmental noise factors that degrade the performance of recognition. In this paper, the echo noise robust HMM learning model using average estimator LMS algorithm is proposed. To be able to adapt to the changing echo noise HMM learning model consists of the recognition performance is evaluated. As a results, SNR of speech obtained by removing Changing environment noise is improved as average 3.1dB, recognition rate improved as 3.9%.