This paper considers the design of linear-phase FIR digital filters that have a variable bandwidth whereas the phase response is fixed. For this purpose, we employ a structure in which the overall transfer function is a weighted linear combination of fixed subfilters and where the weights are directly determined by the bandwidth. We introduce a linear programming design technique which generates globally optimal overall filters in the minimax (Chebyshev) sense. Further, both the cases where the subfilters are of equal and different orders, respectively, are treated. Earlier, only the equal-order case has been considered.
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