Quadrature mirror filter

About: Quadrature mirror filter is a research topic. Over the lifetime, 955 publications have been published within this topic receiving 28900 citations.

Image Encoding with Triangulation Wavelets

Abstract: We demonstrate some wavelet-based image processing applications of a class of simplicial grids arising in finite element computations and computer graphics. The cells of a triangular grid form the set of leaves of a binary tree and the nodes of a directed graph consisting of a single cycle. The leaf cycle of a uniform grid forms a pattern for pixel image scanning and for coherent computation of coefficients of splines and wavelets. A simple form of image encoding is accomplished with a one dimensional quadrature mirror filter whose coefficients represent an expansion of the image in terms of two dimensional Haar wavelets with triangular support. A combination the leaf cycle and an inherent quadtree structure allow efficient neighbor finding, grid refinement, tree pruning and storage. Pruning of the simplex tree yields a partially compressed image which requires no decoding, but rather may be rendered as a shaded triangulation. This structure and its generalization to n-dimensions form a convenient setting for wavelet analysis and computations based on simplicial grids. keywords: wavelets, image encoding, image compression, image scanning, filtering, triangulation, binary trees.

Near Perfect Reconstruction Quadrature Mirror Filter

Abstract: In this paper, various algorithms for designing quadrature mirror filter are reviewed and a new algorithm is presented for the design of near perfect reconstruction quadrature mirror filter bank. In the proposed algorithm, objective function is formulated using the perfect reconstruction condition or magnitude response condition of prototype filter at frequency (ω = 0.5π) in ideal condition. The cutoff frequency is iteratively changed to adjust the filters coefficients using optimization algorithm. The performances of the proposed algorithm are evaluated in term of computation time, reconstruction error and number of iterations. The design examples illustrate that the proposed algorithm is superior in term of peak reconstruction error, computation time, and number of iterations. The proposed algorithm is simple, easy to implement, and linear in nature. Keywords—Aliasing cancellations filter bank, Filter banks, quadrature mirror filter (QMF), subband coding.

Digital chromatic dispersion compensation in coherent transmission system using a time-domain filter

Abstract: We demonstrate the chromatic dispersion equalization employing a time-domain filter in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent system. The required tap number of the filter is analyzed from anti-aliasing and pulse broadening. The dynamic range of the filter is evaluated by using different number of taps.

Frequency-mixing method and frequency-mixing device using the same

Abstract: A frequency-mixing method includes a step of generating a first quadrature signal having a predetermined frequency, a second quadrature signal having a phase difference of about 180 degrees with respect to a phase of the first quadrature signal, a third quadrature signal having a phase difference of about 90 degrees with respect to the phase of the first quadrature signal and a fourth quadrature signal having a phase difference of about 90 degrees with respect to a phase of the second quadrature signal; a step of controlling a phase of the third quadrature signal and a phase of the fourth quadrature signal so as to control a linearity of a frequency mixer; and a step of down-converting a radio frequency (RF) signal using the first through the fourth quadrature signals. Accordingly, performance of a direct-conversion receiver (DCR) can be improved by employing a frequency-mixing device capable of enhancing a linearity of a frequency mixer.