Portland State University. Department of Electrical Engineering.
Date of Publication
Master of Science (M.S.) in Electrical and Computer Engineering
Electrical and Computer Engineering
Digital electric filters -- Design and construction, Mathematical optimization -- Computer programs, Iterative methods (Mathematics), Nonlinear programming
1 online resource (vii, 78 p.)
In practice, an IIR filter can distort the information content of the signal because of its inherent non-linear phase characteristics introduced through the design of the filter. If the the receiver of the signal is the human ear, e.g., when a speech or music signal is to be processed, phase distortion is quite tolerable. But, in other applications it can be rejected as phase characteristics is required to be fairly linear. Applications of this type include data transmission, where the signal is to be interpreted by digital hardware, and image processing, where the signal is used to reconstruct an image that is to be interepted by the human eye. This thesis deals with the problem by introducing an all-pass equalizing filter, whose magnitude response is unity, in cascade with the given filter to produce the same filter magnitude but with a linear-phase instead. This accomplished by solving the problem of minimizing the approximation error for the group delay by using a suitable optimization algorithm, the free parameters (poles and zeros) are varied in a way to minimize the approximation error according to the assumed error criterion. Those set of parameters found after optimization determines the desired linear filter.
Khodor, Rabih, "Equalization of a Non-linear Phase of a Low-pass Filter" (1996). Dissertations and Theses. Paper 5317.