An alternate technique for min-max design of multiband finite impulse response digital filters

The practical issue addressed in this paper is the automated design of FIR multiband digital filters. The specific theoretical filter-design problem addressed is what to do over the transition regions if a min-max design criterion is adopted. The technique suggested consists of formulating the design over the entire band [0,π]. Advantages and disadvantages of this approach versus the use of "don't care" bands are examined. Specific comparisons pertaining to FIR multiband design are presented. The specific contribution of the paper is twofold: (i) A suggestion for the type of functions to use as an objective over the transition regions if a full band [0,π] min-max formulation is to be used. (ii) A design technique for multiband FIR which appears useful in a CAD context. This technique gives results comparable to those obtained with the "don't care" band approach. However, the new procedure requires less user interaction and is thus much easier to automate.