Designing near linear phase recursive filters using linear programming

Previous linear programming design techniques have concentrated on magnitude only specifications, In the technique presented here we design the filter to prescribed real and imaginary components of the frequency domain specifications. Although general phase characteristics have proved difficult to achieve, good results are obtained for constant group delay designs. The technique employed is to alter the value of the group delay in the specifications until a minimum error is achieved. Stable designs can be established by employing usual stability criteria. Results of the design technique are presented and an extension to two dimensional filter designs is discussed.