On hybrid filter bank A/D converters with arbitrary over-sampling rate

Hybrid filter banks (HFB) analog/digital (A/D) systems permit wide-band, high frequency conversion. This paper presents a method for designing output digital filters of the HFB, when analog input filters are easy-to-implement (typically second order) and consequently can work at high rate. The constraint of quantization noise amplification due to the digital output filters is taken into account by using the Lagrange multiplier method. In order to improve quality of the output signal in spite of this constraint, degrees of freedom are added by using a K-channels HFB associated with an oversampling factor M less than K and by imposing a condition stronger than that of Nyquist on the input signal.