• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.698-704
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• 2013

The image process for image enhancement applies differently the same algorithm for each application. So, the optimized value for each application is required. In this paper, the X-ray medical image using a high-pass filter was improved edges. The result image was improved edge and the contrast of flat area using a constant multiplier and offset. Therefore, the high-frequency emphasis filter optimized for medical image is required. These optimized values are the gaussian high-pass filter, the distance of cutoff frequency=0.05 and offset=0.5. From the result of optimaized simulation, The proposed method has enhanced contrast and edge of the image in the contrast of existing mothods.

• Journal of the Korean Society of Radiology
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• v.8 no.6
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• pp.301-307
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• 2014

In this study, an image acquired by the DSA(Digital Subtraction Angiography) system that is configured to configure the algorithm for high pass filtering algorithm experiments to improve the quality of angiography methods proposed. high pass filter is a high-frequency components pass through the filter, blocking low-frequency components. Part of the boundary line and contour of the organ corresponds to the high-frequency component is a high-frequency component of a medical image. Therefore, the high pass filter is also used for detection of the boundary line, but is also used for the high frequency enhancement. It was able to be analyzed by the proposed algorithm, to improve the quality of the angiography. Found out that the expression of the target site stand out clearly. The quality of the DSA system proposed in the wrong diagnosis software can be used to reduce, it is possible to develop and will further improve the accuracy of the treatment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.91-99
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• 2018

This paper has proposed a low-noise and high-linear RF receiver supporting TV white space from 470 MHz to 698 MHz), which is implemented in $0.13-{\mu}m$ CMOS technology. It consists of a low-noise amplifier, a RF band-pass filter, a RF amplifier, a passive down-conversion mixer, and a channel-selection low-pass filter. A low-noise amplifier and RF amplifier provide a high voltage gain to improve the sensitivity level. To suppress strong and nearby interferers, two RF filtering schemes have been performed by using a RF BPF and a down-conversion mixer. The proposed LPF has been based on the common-gate topology and adopted a bi-quad cell to achieve -24dB/oct characteristics. In addition, the RF receiver can support the overall TV band by controlling a LO frequency. The simulated results show a voltage gain of 56 dB, a noise figure of less than 2 dB, and an out-of-channel IIP3 of -2.3 dBm. It consumes 37 mA from a 1.5 V supply voltage.

• ETRI Journal
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• v.14 no.4
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• pp.249-257
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• 1992

인버터를 이용한 대역 통과 필터를 설계할 때, 기존에 사용하던 기하평균 방법은 인버터의 이미턴스가 주파수에 대해 일정하다고 생각한 가정때문에 대역폭률이 10% 이상인 광대역 필터에서 대역폭과 중심주파수가 잘 맞지 않게 된다. 이에 대한 보완으로 Cohn은 새로운 함수를 제안하였는데, 이 함수도 coupling 방법에 따른 사용상의 제약을 갖고 있다. 본 고에서는 coupling 방법에 관계없이 광대역 필터를 설계할 수 있는 새로운 변환 함수를 제시하였으며 컴퓨터 시뮬레이션을 통해 기존의 함수들보다 더 정확하다는 것을 확인하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.238-241
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• 1998

성문파 신호로부터 음원변수들을 추출하는 방법과 그 전 단계에서 역 필터링 방법에 의해 구한 미분성문파 신호로부터 고주파 잡음을 제거하기 위해 음원구간에 따라 필터의 대역폭을 달리함으로서 음원변수 추출과정에서 저역통과 필터에 의해 발생할 수 있는 오차를 최소화하기 위한 선택적 저역통과 필터링 방법을 제안한다. 이 방법은 음원모델중 하나인 LF-model 펄스를 합성하여 필터링 함으로서 그 성능을 비교, 평가하였다.

• Journal of Broadcast Engineering
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• v.1 no.2
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• pp.118-132
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• 1996

This paper proposes a wavelet transform- based image compression method using the energy distribution. The proposed method Involves two steps. First, we use a wavelet transform for the subband decomposition. The original image Is decomposed into one low resolution subimage and three high frequency subimages. Each high frequency subimages have horizontal, vertical, and diagonal directional edges. The wavelet transform is luther applied to these high frequency subimages. Resultant transformed subimages have different energy distributions corresponding to different orientation of the high pass filter. Second, for higer compression ratio and computational effciency, we discard some subimages with small energy. The remaining subimages are encoded using either DPCM or quantization followed by entropy coding. Experimental results show that the proposed coding scheme has better performance in the peak signal to noise ratio(PSNR) and higher compression ratio than conventional image coding method using the wavelet transform followed by the straightforward vector quantization.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.08a
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• pp.138-141
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• 2008

본 논문에서는 영상의 화질 개선을 위해 일반적으로 사용되는 방법인 미디안 필터와 샤프닝 필터의 단점들을 개선한 알고리즘을 제안한다. 제안하는 방법은 영상의 통계적 정보를 이용하여 평탄영역과 평탄하지 않은 영역을 구분하고 각 영역에 대해 저주파 통과 필터와 고주파 통과필터를 각기 다르게 적용하여 기존의 다른 화질 개선 필터 보다 향상된 개선 효과를 기대 할 수 있다. 또한 적용할 스케일 값의 크기만 결정하면 각 화소에서의 범주와 세기는 영상의 통계적 정보를 이용한 매핑 함수를 통해 자동으로 생성된다. 따라서 기존의 미디안 필터와 샤프닝 필터가 가지고 있던 복잡한 파라메터의 설정과정이 필요 없이 평탄영역에서의 잡음제거 및 블러링 효과와 활동성이 높은 영역에서의 선명화 효과를 동시에 얻을 수 있다.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.22-27
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• 2014

Blocking and ringing artifacts continue to be the most serious defects that occur in images and video streams compressed to low bit rates using block-based discrete cosine transform(DCT) compression standards. These artifacts contain the high frequency components near the block and the edge boundaries. Usually the lowpass filter can remove them. However, simple lowpass filter results into blur by removing important information such as edges at the same time. To overcome these problems, we propose a novel postfiltering algorithm that calculate the weight value based on the intensity similarity in the neighboring pixels and multiply this weight to the Gaussian lowpass filter coefficient. Experimental results show that the proposed technique provides satisfactory performance in both objective and subjective image quality.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.2
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• pp.200-207
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• 2009

This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and Step-Impedance-Open-Stub(SIOS). The SIOS can be reduce length about 30 % more than general 0.25 $\lambda$ open stub. And the stub can the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter has 3 dB fractional bandwidth of 51.75 %(3.206 GHz), an insertion loss of better than 0.44 dB from 4.587 GHz to 7.793 GHz, and two rejection of greater than 30 dB within 221 MHz($4.326{\sim}4.587\;GHz$) at low frequency band, 181 MHz($7.739{\sim}7.954\;GHz$) at high frequency band. Maximum rejection characteristics of the filter are -61.8 dB at low frequency and -76.3 dB at high frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.505-513
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• 2004

Most video codecs including the international standards use the block-based hybrid structure for efficient compression. But for low bit-rate applications such as video transmission through wireless channels, the blocking artifacts degrade image qualify seriously. In this paper, we propose an adaptive de-blocking algorithm using characteristics of the block boundaries. Blocking artifacts contain the high frequency components near the block boundaries, therefore the lowpass filtering can remove them. However, simple lowpass filtering results into blurring by removing important information such as edges. To overcome this problem, we determine the modes depending upon the characteristics of pixels adjacent to block boundary then proper filter is applied to each area. Simulation results show that proposed method improves de-blocking performance compared to that of MPEG-4.