Implementation and optimization of a modulated filter bank based on allpass filters.

Abstract

A filter bank based on an allpass IIR filter with brick-wall response was designed by A. J. Van Leest in [17]; however, the delay in the filter bank is too long to be used in real time applications. In order to reduce the delay, the orders of coefficients, transition bandwidth and filter bank structures must be optimized. The order of coefficients can be reduced by increasing the stopband attenuation. In order to further reduce the delay, the sharpness of the filter bank has to be reduced. This thesis also discussed the number of band and filter bank structure against to filter bank delay. The filter bank can be used in non-real time application such as CD compression with high order coefficient. The minimum transition bandwidth can be reached at 0.03257pi/number of band. This thesis expands upon DCT modulations of IIR based modulated filter banks and investigate the Hartley transformation in filter bank modulation as a new modulation technique. These modulation techniques generate the real output signal with real input signals. The quantization errors from quantizing the coefficient are studied. It is concluded that at least 16 bits are required in order for a filter bank to give a good performance as designed without quantization.