FFT-Based multirate signal processing for 18-band Quasi-ANSI S1.11 1/3-Octave Filter Bank

For characteristic analysis of the 24 KHz audio, the 10-ms, 18-band quasi-ANSI filter bank has been proposed and designed for advanced hearing aids. To greatly reduce the computation complexity, several time-domain multirate signal processing techniques, such as the up- and down-sampling rate conversions and the interpolated finite impulse response (IFIR) filters, were investigated. However, it is well known that using fast Fourier transform (FFT) to perform the linear convolution can dramatically reduce the computational complexity. Taking both advantages, in this brief we investigated the FFT-based multirate signal-processing technique and explored their efficient architecture. To demonstrate the success of the proposed architecture, we implemented a real-valued FFT-based 10.7-ms, 18-band quasi-ANSI 1/3-octave filter bank using TSMC 90-nm CMOS high-VT technology. We found that, for each input sample, the proposed FFT-based quasi-ANSI 1/3-octave filter bank used approximately 77% fewer multiplications than the previous time-domain design. The proposed FFT-based quasi-ANSI filter bank was operated at 13 MHz to process the 24-KHz audio in real time, and it consumed only 14 μW (@0.9V) of dynamic power.