An effective reduction of subproblems in design of CSD coefficient FIR filters

In this paper, an effective reduction method of the number of subproblems for the design of CSD (Canonic Signed Digit) coefficient FIR (Finite Impulse Response) filters using BB (Branch and Bound method) is studied. The problem can be formulated as a mixed integer programming problem. The problem can be optimally solved by using the BB. For solving the problem, it is required to solve a large number of subproblems, and it causes a high computational time. Recently, a novel method for the reduction of the number of subproblems has been proposed. In the method, the subproblems can be reduced by starting from an initial branch tree constructed by an approximate solution obtained by any heuristic method. However, the reduction of subproblems depends on the heuristic method applied. In this paper, the effective methods for the reduction of subproblems are studied. Several examples are shown to present the efficiency of the studied methods.