• Journal of KIISE:Computing Practices and Letters
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• v.14 no.6
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• pp.604-608
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• 2008

The TFT-LCD image allows non-uniform illumination variation and that is one of main difficulties of finding defect region. The SQI (self quotient image) has the HPF (high pass filter) shape and is used to reduce low frequency-lightness component. In this paper, we proposed the TFT-LCD defect-enhancement algorithm using characteristics of the SQI, that is the SQI has low-frequency flattening effect and maintains local variation. The proposed method has superior flattening effect and defect-enhancement effect compared with previous the TFT-LCD image preprocessing.

• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.51-60
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• 2009

This paper presents a new method of designing room equalization filters using a warped common acoustical pole and zero (WCAPZ) modeling. The proposed method is capable of significantly reducing the order of the equalization filters without sacrificing the filter performance, especially, at low frequencies. Thus, the associated input-output delay is much smaller than the conventional block transform method while its computational complexity is comparable to it. The computational complexity also is still comparable to the conventional room equalization method, since the filter is implemented in the linear frequency domain after the pole-zero dewarping. Simulation results confirm that the use of the proposed algorithm significantly improves the room equalization over a range of low frequencies.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.167-176
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• 1993

The high resolution studies for shallow seismic reflection are carried out using 24-channel seismograph and the high sensitivity geophone(50-500Hz). In order to study the underground structures such as small faults, fractures, cracks and cavities, it is of great importance to enhance high resolution of the seisrnic records for the targets vertically and laterally. In analysis of high resolution seismic reflection, Nyquist frequency($F_N$) should be lager than the highest frequency in the records and the highest wave number should not be exceed the Nyquist wave number($1/2{\Delta}x$). The highest frequency above the Nyquist will be removed using low pass filter or antialias filter. The trace interval Ax should be taken into account so that the highest wave number(f/v) can be less than $1/2{\Delta}x$. The Fraunhofer diffraction of a hyperbola seismic section above the tunnel appeares on the common offset method, and little first arrivals of direct wave on the single-end shooting, delayed strong impulsive reflections are also shown above the tunnel. Ray Method(Cherveney and Psencik, 1983) also represents the same results that the reflected waves from the tunnel are delayed and single impulsive with little first arrivals, while transrnitted waves through the tunnel are delayed with low frequency.

• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.269-278
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• 1998

This paper describes a development of efficient stress ECG signal analysis algorithm. The algorithm consists of wavelet adaptive filter(WAF), QRS detector and ST segment detector. The WAF consists of a wavelet transform and an adaptive filter. The wavelet transform decomposed the ECG signal into seven levels using wavelet function for each high frequency bank and low frequency bank. The adaptive filter used the signal of the seventh lowest frequency band among the wavelet transformed signals as primary input. For detection of QRS complex, we made summed signals that are composed of high frequency bands including frequency component of QRS complex and applied the adaptive threshold method changing the amplitude of threshold according to RR interval. For evaluation of the performance of the WAF, we used two baseline wandering elimination filters including a standard filter and a general adaptive filter. WAF showed a better performance than compared filters in the noise elimination characteristics and signal distortion. For evaluation of WAF showed a better performance than compared filters in the noise elimination characteristics and signal distortion. For evaluation of results of QRS complex detection, we compared our algorithm with existing algorithms using MIT/BIH database. Our algorithm using summed signals showed the accuracy of 99.67% and the higher performance of QRS detection than existing algorithms. Also, we used European ST-T database and patient data to evaluate measurement of the ST segment and could measure the ST segment adaptively according to change of heart rate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.127-129
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• 2012

Due to the prevalence of digital camera, multi-media etc. the image is being used in everyday life. However, noise always damages the image and the image denoising technology is important part for improving the image visual quality. There are many existing methods to remove noise such as wiener filter, mean filter and VisuShrink etc. However, they perform not good enough for denoising. Hence, in this paper we proposed a hybrid filter algorithm which consists of wiener filter and modified wavelet based thresholding method using adaptive threshold and thresholding function. The proposed algorithm shows not only better low frequency and high frequency property, but also the outstanding noise suppression and edge preservation properties.

• Journal of Korea Multimedia Society
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• v.2 no.1
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• pp.30-37
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• 1999

A wideband active noise cancelling system involves adaptive filters with hundreds of taps. The computational burden required with these long adaptive filters. This paper presents active noise cancelling system using M-channel QMF filter banks in which the adaptive weights are computed in subbands. The analysis and synthesis filter banks use cosine-modulated pseudo QMF filters. The reference signal for on-line identification of error path transfer characteristics is used to difference signal between the output of adaptive filters and the output of lowpass subband filters. The proposed adaptive subband filter bank suggests robust active noise cancelling system retaining the computational complexity and convergence speed advantaged of subband processing.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.4
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• pp.227-236
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• 2003

This paper proposes a modified jointly-blue noise mask (MJBNM) method using the S-CIELAB color measure as digital color halftoning method. Based on an investigation of the relation between the pattern visibility and the chromatic error, of a blue noise pattern, a halftoning method is proposed that reduces the chromatic error, while preserving a high quality blue noise pattern. Accordingly, to reduce the chrominance error, the low-pass filtered error and S-CIELAB chrominance error are both considered during the mask generation procedure and calculated for single and combined patterns. Using the calculated low-pass filtered error, the patterns are then updated by either adding or removing dots from the multiple binary patterns. Finally, the pattern exhibiting the lower S-CIELAB chrominance error is selected. Experimental results demonstrated that the proposed algorithm can produce a visually pleasing half toned image with a lower chrominance error than the JBNM method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.584-588
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• 2021

The impedance of the speaker is likely to be recognized as a fixed value. However, speaker impedance continues to vary with frequency variation, especially larger in resonant frequency region. The sound pressure level of loudspeakers is determined by the current flowing throughout the coil that consists loudspeakers. If loudspeakers are driven by voltage, sound pressure level of the loudspeaker is distorted by the variation of loudspeaker impedance. Current-drive of loudspeakers can solve this problem, but distortion of sound pressure level occurs in low frequencies due to resonance. The distortion can degrade the sound quality of the sound system. So to solve this problem, In this paper, we propose a resonance compensation circuit using DSP. we simulates audio systems using an equivalent model of loudspeakers to verify distortion of sound pressure level due to impedance variation and propose a circuit to compensate it. The proposed circuit is configured using a state variable filter and it can adjust the center frequency and output, so it will be used various sound systems.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1179-1182
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• 1998

광대역 능동잡음제거는 수 백개의 적응필터 탭 수를 갖는다. 탭 수가 긴 적응필터는 많은 계산량이 요구된다. 본 논문에서는 적응계수 벡터가 서브밴드로 계산되는 M-채널 QMF 필터뱅크와 적응필터를 이용한 자동차 소음제거 모델을 제안한다. 분해 필터뱅크와 합성 필터뱅크는 cosine-modulated pseudo QMF 필터를 사용한다. 오차경로의 전달특성을 온라인 인식하기 위한 기준신호는 적응필터의 출력신호와 저주파대역의 서브밴드 출력신호와의 차신호를 사용한다. 따라서 제안한 자동차 소음제거 모델은 계산량이 적고 수렴속도가 빠른 견실한 시스템이 되도록 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.636-644
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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) for wireless data communication. The SIOS can be reduce length about 30% more than general $0.25{\lambda}$ 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 3dB fractional bandwith of 52.5%(3.267GHz), an insertion loss of better than 0.33dB from 4.587GHz to 7.854GHz, and two rejection of greater than 30dB within 221MHz$(4.366GHz{\sim}4.587GHz)$ at low frequency band, 181MHz$(7.854GHz{\sim}8.035GHz)$ at high frequency band. Maximum rejection characteristics of the filter are -54dB at low frequency and -60dB at high frequency.