• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.97-102
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• 2000

Subband coding is to divide the signal frequency band into a set of uncorrelated frequency bands by filtering and then to encode each of these subbands using a bit allocation rationale matched to the signal energy in that subband. The actual coding of the subband signal can be done using waveform encoding techniques such as PCM, DPCM and vector quantizer(VQ) in order to obtain higher data compression. Most researchers have focused on the error in the quantizer, but not on the overall reconstruction error and its dependence on the filter bank. This paper provides a thorough analysis of subband codecs and further development of optimum filter bank design using vector quantizer. We compute the mean squared reconstruction error(MSE) which depends on N the number of entries in each code book, k the length of each code word, and on the filter bank coefficients. We form this MSE measure in terms of the equivalent quantization model and find the optimum FIR filter coefficients for each channel in the M-band structure for a given bit rate, given filter length, and given input signal correlation model. Specific design examples are worked out for 4-tap filter in 2-band paraunitary filter bank structure. These optimum paraunitary filter coefficients are obtained by using Monte Carlo simulation. We expect that the results of this work could be contributed to study on the optimum design of subband codecs using vector quantizer.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.1
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• pp.66-69
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• 2009

An adaptive echo canceller is necessary for an application such as a speakerphone, 3G image telephony and VoIP service system. These echo cancellers need to have many taps for filtering echo signals. Many taps cause computation data to increase and convergence speed to be low. To overcome these problems, An adaptive echo canceller with the advanced convergence speed is proposed in this paper. To improve the speed, we divide an echo band into subbands and place a subband filter to be adaptive for each subband. Each subband filter recognizes the echo signal as subband echo signals. So, dynamic range of subband is small, the convergence speed is fast. Moreover, as the number of Tap and weight update are estimated in each subband, the implementation complex of a adaptive filter is low.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.195-201
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• 2005

In this paper, a study of damage measures for truss structures using the Extended Projection filter theory is presented. Many researchers are interested in inverse problems and one of solution procedures for inverse problems that are very effective is the approach using the filtering algorithm in conjunction with numerical solution methods. In this paper, the projection filtering in conjunction with structural analysis is applied to the identification of damages in truss structures. And, the effectiveness of proposed method is verified through the numerical examples of a free vibrating structure.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.185-192
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• 2008

The crosstalk is the most serious problem in playing audio signals with more than two speakers. Usually an inverse filter is employed to remove such a Phenomenon. The LNS method, one of most effective design techniques for an inverse filter, has some advantages such as easy implementation and quick computation. However, the inverse filter designed by the LNS method is not easy to adapt immediately for the delivery system change since the pre-measured impulse response is used to design the filter. In this work, we present an adaptive algorithm for the inverse filter design. With the present algorithm. the inverse filter is initially designed by the LNS methods and continuously adjusted to cope with the delivery system changes. To verify the proposed method. some simulations were carried out and the results confirmed that the performance of the crosstalk calculation can be improved in entire frequency range.

• 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 Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.759-761
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• 2001

한반도 동해의 외해역(울릉도) 및 내해역에서(포항 및 묵호)의 조사된 T/P 해면자료와 TG해면자료간의 상관성이 각각 어떻게 나타나는가를 파악하기 위하여 본 연구를 수행하였다. 이때의 1992년 10월부터 1997년 12월까지 관측된 T/P자료와 TG자료를 각각 이용하였다. 본 연구로부터 우리는 다음과 같은 몇 가지 결과를 알 수 있었다. 1) 비교적 조석의 영향이 우세한 내해역에 위치한 포항 및 묵호가 외해역에 위치한 울릉도에 비해서 낮은 상관성을 보였다. 이러한 큰 차이는 M2, S2, Kl 분조 등에 의한 조석변형 때문에 발생하는 현상이다. 이것은 주로 T/P자료에 기인하는 조석오차이다. 2) 조석변형 때문에 발생하는 신호는 해양신호와 관계없는 잘못된 거짓신호로서 이를 제거하기 위해서는 lowpass filter를 적용하는 것이 좋다. 대체로 외해역의 경우는 60일, 120일, 180일, 200일의 필터를 순차적으로 처리함에 따라 상호 두 자료간의 유의성이 점차적으로 개선되는 것을 알 수 있었으나, 내해역의 경우에는 거의 유의성이 개선되지 않는 것으로 나타났다. 3) 200일의 필터를 처리했을 때, 외해역에 위치한 울릉도는 상관값이 0.91로 매우 높은 유의성을 보였고, 그리고 내해역에 위치한 포항 및 묵호는 각각 0.58 및 0.65로서 울릉도에 비해서 상대적으로 낮은 유의성을 보였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.57-58
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• 2014

Digital filter is very important role in signal processing system. In general, input signal is determined by transfer function of the digital filter. But if input signal was exposured in various sound environment, it is difficult to verify its original source. In this paper, inverse problem in order to extract original input signal from noisy environment is considered.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.107-113
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• 2017

This paper provides a new approach for modeling of vector quantizer(VQ) followed by analysis and design of subband codecs with imbedded VQ's. We compute the mean squared reconstruction error(MSE) which depend on N the number of entries in each codebook, k the length of each codeword, and on the filter bank(FB) coefficients in subband codecs. We show that the optimum M-band filter bank structure in presence of pdf-optimized vector quantizer can be designed by a suitable choice of equivalent scalar quantizer parameters. Specific design examples have been developed for two different classes of filter banks, paraunitary and the biorthogonal FB and the 2 channel case. These theoretical results are confirmed by Monte Carlo simulation.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.204-208
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• 2003

In this paper, a new matrix vector formulation for a wavelet-based subband decomposition is introduced. This formulation provides a means to compute a regular multi-resolution analysis over many levels of decomposition. With this approach. any single channel linear space-invariant filtering problem can be cast into a multi-channel framework. This decomposition Is applied to the linear space-invariant image restoration problem and propose a frequency-adaptive constrained least squares(CLS) filter. In the proposed filter, we use different parameters adaptively according to subband characteristics. Experimental results are presented for the proposed frequency-adaptive CLS filter These experiments show that if accurate estimates of the subband characteristics are available, the proposed frequency adaptive CLS filter provides significant improvements over the traditional single channel filter.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.60-65
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• 2010

In this paper, we propose a dual-band filtering method optimized to DBO-CSS systems which are alternatively transmitted in low and high bands. The conventional channel filter which passes entire signal bandwidth causes a problem that excessive noise in neighboring sub-band is added while one of signals in two sub-bands is received. The dual-band filtering proposed in this paper can overcome the performance degradation in the conventional filtering method without increase of hardware complexity. The proposed method is based on two filters to be matched with DBO-CSS signals receiving alternatively and can exclude the undesired noise in neighboring sub-band. Simulation results for the proposed method show better performance about 2.5dB than the conventional one.