Oversampling complex-modulated digital filter bank pairs suitable for extensive subband-signal amplification

Oversampling, complex-modulated digital subband coder fil ter banks are commonly adopted in modern hearing aids to allow fo r individual amplification of subband signals in order to comp ensate for hearing losses of impaired persons. Minimum power consu mp- tion and low group delay have been the main concern in the desi gn of these filter banks. Guaranteeing frequency-independentand low group delay in case of subband-signal amplification has, how ever, been neglected in the past. In this contribution, we investigate the delay and amplifica tion properties of oversampling complex-modulated FIR filter ba nks in case of extensive subband signal amplification. Based on the se re- sults, a sufficient condition for constant group delay is der ived. Fur- thermore, we present a compensation method which allows for con- stant group delay, even if the sufficient condition is violated. An illustrative design example demonstrates the potential ofthe com- pensation method.