• 제목/요약/키워드: 웨이브렛 필터

검색결과 92건 처리시간 0.02초

Orthogonal Wavelet Construction using Recursive Filter Bank (재귀형 직교 웨이브렛 함수)

  • Do, Jae-Su
    • The KIPS Transactions:PartB
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    • 제8B권4호
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    • pp.395-402
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    • 2001
  • 본 논문에서는, 1차원 및 2차원 웨이브렛 함수를 전역통과필터(APF)와 지연기의 병렬접속에 위한 재귀형(IIR) 디지털 필터로 구성하는 방법을 제안한다. Mallat에 의하여 웨이브렛 변환과 필터뱅크가 밀접한 관계에 있다는 것이 알려졌고, 완전 재구성 필터뱅크로부터 웨이브렛 함수를 도출하는 다양한 방법이 알려져 있다. 그러나, 이러한 방법의 대부분은 비재귀형(FIR) 디지털 필터에 근거를 두는 것으로, 재귀형 디지털 필터에 의한 방법은 거의 제안되어 있지 않다. 재귀형 필터를 이용하는 장점은 비재귀형에 비하여 낮은 차수로 표현되는 점이다. 또 직교 웨이브렛 함수를 끌어내기 위한 직교조건을 용이하게 만족시킬 수 있다. 본 논문에서는 웨이브렛 함수에 요구되는 레귤레리티(Regularity)조건을 만족시키기 위하여, 최대 평탄성(Maximally Flat)을 부가한 새로운 1차원 및 2차원 재귀형 웨이브렛 함수의 도출법을 보인다.

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Optimal Wavelet Filter Design Using Coding Gain (압축이득을 이용한 최적 웨이브렛 필터의 설계)

  • 이임건
    • Journal of Korea Multimedia Society
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    • 제6권7호
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    • pp.1159-1168
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    • 2003
  • In this paper, a new wavelet filter design algorithm is proposed which optimizes energy compaction of transformed coefficients. The filter, designed by the proposed algorithm enhances the coding gain of the system with fixed quantizer by most unevenly distributed energy in transform domain. The coding gain function was extended to obtain the optimal filter coefficients in each stage. The experiments showed that the filter designed by proposed method outperforms conventional filters in energy compaction rate.

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Characteristic of Inverse wavelet transform and Multi bank system (연속 웨이브렛 역변환의 특성 및 멀티 뱅크 시스템)

  • Kim Tae-hyung;Yoon Dong-han
    • Journal of the Korea Institute of Information and Communication Engineering
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    • 제9권2호
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    • pp.229-236
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    • 2005
  • This paper is contribute to Inverse continuous wavelets transform(ICWT) which permits to determine real 'time-scale' plan. The application of ICWT is not yet represented because of the numerical difficulty. If the signal can be reconstructed stably by ICWT, the multi scale filter bank system which composed by analysis and synthesis process can be designed. In this work, we represent the ICWT which leads to nearly perfect reconstruction of signal and the multi-scale filter bank system.

Analysis of the multiwavelet filter bank architecture (멀티웨이브렛 필터뱅크의 구조 분석)

  • Heo, Ung;Choi, Jae-Ho;Park, Tae-Yoon;Lee, Cheol-Soo
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • 한국신호처리시스템학회 2003년도 하계학술대회 논문집
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    • pp.209-212
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    • 2003
  • In this paper, we have analyzed a multiwavelet filter bank architecture which have several bases. The filter bank composed of multiwavelets bases is matrix-valued. Multiwavelets offer simultaneous orthogonality, symmetry, and short support, which is not possible for the scalar wavelet system, hence multiwavelet system can obtain excellent performance in signal analysis and compress. Also the multiwavelet differs from the scalar wavelet system in requiring two or more input streams to the multiwavelet filter bank. In this paper, we describe methods for obtaining such a input stream and how apply the actual data.

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Flaw Detection of Ultrasonic NDT in Heat Treated Environment Using WLMS Adaptive Filter (열처리 환경에서 웨이브렛 적응 필터를 이용한 초음파 비파괴 검사의 결함 검출)

  • 임내묵;전창익;김성환
    • The Journal of the Acoustical Society of Korea
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    • 제18권7호
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    • pp.45-55
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    • 1999
  • In this paper, we used the WLMS(Wavelet domain Least Mean Square) adaptive filter based on the wavelet transform to cancel grain noise. Usually, grain noise occurs in changes of the crystalline structure of metals in high temperature environment. It makes the detection of flaw difficult. The WLMS adaptive filtering algorithm establishes the faster convergence rate by orthogonalizaing the input vector of adaptive filter as compared with that of LMS adaptive filtering algorithm in time domain. We implemented the WLMS adaptive filter by using the delayed version of the primary input vector as the reference input vector and then implemented the CA-CFAR(Cell Averaging- Constant False Alarm Rate) threshold estimator. CA-CFAR threshold estimator enables to detect the flaw and back echo signals automatically. Here, we used the output signals of adaptive filter as its input signal. To Cow the statistical characteristic of ultrasonic signals corrupted by grain noise, we performed run test. The results showed that ultrasonic signals are nonstationary signal, that is, signals whose statistical properties vary with time. The performance of each filter is appreciated by the signal-to-noise ratio. After LMS adaptive filtering in time domain, SNR improves to about 2-3㏈ but after WLMS adaptive filtering in wavelet domain, SNR improves to about 4-6㏈.

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Denosing of images using locally adaptive wiener filter in wavelet domain (웨이브렛 변환 영역에서의 국부적응 Wiener 필터에 의한 영상 신호의 잡음 제거)

  • 장익훈;김남철
    • The Journal of Korean Institute of Communications and Information Sciences
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    • 제22권12호
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    • pp.2772-2782
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    • 1997
  • In this paepr, a Wiener filtering method in wavelet domain is proposed for restoring an image corrupted by additive white noise. The proposed method utilizes the characteristics of wavelet transform signals and the local statistics of each subband. When estimating the local statistics in each subband, the size of filter window is varied according to each scale. At this point, the local statistics in each wavelet subband is estimated only by using pixedls which have similar statistical property. Experimental results show that the proposed method has better performance over the conventional Lee filter with a window of fixed size.

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Topographic Analysis Using Wavelet-Based Digital Filters in the KR5 area, NE Equatorial Pacific (웨이브렛 디지털 필터를 이용한 북동태평양 KR5 지역의 지형 분석방법)

  • Jung, Mee-Sook;Lee, Tae-Gook;Kim, Hyun-Sub;Ko, Young-Tak;Park, Cheong-Kee;Kim, Ki-Hyune
    • Journal of the Korean Geophysical Society
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    • 제9권4호
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    • pp.311-320
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    • 2006
  • Digital filters designed using wavelet theory are applied to bathymetry data acquired from KR5 area of Korea Deepsea Mining Area. The filters used in this study are the linear B-spline wavelet filter and derivative of a Cubic B-spline filter. With proper tuning of the digital filters, we can identify the location and orientation of the abyssal hill and abyssal trough in bathymetry. These features obtained from the digital filters are well correlated with bathymetric image. This quantitative information, which can be used to understand the underlying geophysical processes, can be further processed to obtain the spacing, orientation and distribution of the abyssal hill. This wavelet analysis of bathymetry provides good data to select the mining site.

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Optical Wavelet POfSDF-FSJTC for Scale Invariant Pattern Recognition with Noise (잡음을 갖는 물체의 크기불변인식을 위한 광 웨이브렛 POfSDF-FSJTC)

  • Park Se-Joon;Kim Jong-Yun
    • The Journal of the Korea Contents Association
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    • 제4권4호
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    • pp.205-213
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    • 2004
  • In this paper, we proposed a wavelet phase-only filter modulation synthetic discriminant function joint transform correlator(WPOfSDF-JTC) for scale invariant pattern recognition, and an improved algorithm to reduce the filter synthesis time. Computer simulation showed that the proposed filter has better SNR than CWMF if input image has random noise and the improved synthesis algorithm can reduce the iteration time. We used frequency selective JTC to solve the problem of the optical alignment and eliminate the autocorrelation and crosscorrelation between each input image.

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A Study on Mixed Filter Algorithm for Restoration of Image Corrupted by AWGN (AWGN에 훼손된 영상복원을 위한 복합 필터 알고리즘에 관한 연구)

  • Yinyu, Gao;Kim, Nam-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • 제16권5호
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    • pp.1064-1070
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    • 2012
  • Nowadays, image processing has been applied in a variety of fields. In order to preserve the high quality of visual the degradation phenomenon for images should be removed. Noise is one of the representative elements cause of the degradation phenomenon and AWGN(additive white Gaussian noise) always damages images. In this paper, an mixed filter algorithm, which is based on parallel denoising method, is proposed to suppress AWGN. This algorithm parallels the spatial domain wiener filter and the wavelet domain thresholding method which thresholding function is selected based on scale level. The proposed modified thresholding function which considers the dependency between parent and child coefficient performs well on suppressing noise.

Improvement of Frequency Characteristics of Boundary Filter for 2-band Orthogonal Wavelet Transform using Zero Inserting Method (영점 삽입 방법을 이용한 2-대역 직교 웨이브렛 변환의 경계필터 주파수 특성 개선)

  • 권상근;박원우
    • Journal of the Korea Institute of Information and Communication Engineering
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    • 제7권6호
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    • pp.1229-1235
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    • 2003
  • When finite length image signal is decomposed into 2-band signal and synthesized using 2-band orthogonal wavelet transform, boundary signals are not reconstructed perfectly. To reconstruct them perfectly, the filters which are different from wavelet filter are applied to the boundary signals. Since the existing boundary filters show poor frequency characteristic, the improvement of performance is bounded in practical applications. In this paper, the design method of improvement of frequency characteristic is proposed using inserting a zero to boundary filters which can reconstruct the boundary regions perfectly. Even though the length of proposed boundary filters is shorter, they show 4.2dB∼6.59dB gains in pass band and stop band error power compared with existing boundary filters. But synthesis process is some complicated.