Linear phase bandpass digital filters with variable cutoff frequencies

A low-pass-to-bandpass transformation for linear phase FIR filters is discussed. The transformed bandpass filter is implemented in a network structure in which the cutoff frequencies are controlled through two parameters. The range through which the cutoff frequencies of the transformed filter can be varied depends on the cutoff frequency and the stopband edge frequency of the prototype low-pass filter. For a given prototype filter, this range is obtained from a set of simple graphs.