Implementação de equalizadores Allpass para correção de atraso de grupo empregando técnicas de otimização

Abstract

Abstract: This dissertation presents the development of an algorithm using optimization methods to obtain stable allpass filters to act as group delay equalizer. The algorithm returns the coefficients of an allpass filter with a prescribed group delay response. The design of this algorithm involved constrained and unconstrained optimization methods. Initially, was implemented the minimax algorithm using a pratical Quasi-Newton algorithm, proposed by Andreas Antoniou [Ant93], for error minimization. After that, a constrained algorithm was to guarantee the filter's stability. extensive tests in the final algorithm with different input data, and different group delay characteristic show that it reaches good results of error minimization and return recursive filters with few coefficients, proving to be a successful design. The dissertation details all the steps, techiniques and equations used to obtain the final algorithm and it still shows some results and simulation proving its feasibility and efficiency. The motivation for this work was the necessity to obtain a stable allpass filter with a prescribed group delav mask, necessary to pre-correct the delay distortion caused by TV receivers.