  In this paper, the design of a computationally efficient variable bandpass
digital filter is presented. The center frequency and bandwidth of this filter
can be changed online without updating the filter coefficients. The warped
filters, obtained by replacing each unit delay of a digital filter with an
allpass filter, are widely used for various audio processing applications.
However, warped filters fail to provide variable bandwidth bandpass responses
for a given center frequency using first order allpass transformation. To
overcome this drawback, our design is accomplished by combining warped filter
with the coefficient decimation technique. The design example shows that the
proposed variable digital filter is simple to design and offers a total gate
count reduction of 36% and 65% over the warped filters compared to the designs
presented in [3] and [1] respectively
