Least squared error FIR filter design with spline transition functions

The authors propose the use of transition bands and transition functions in the ideal amplitude frequency response of a linear finite impulse response phase (FIR) digital filter to allow the analytical design of optimal least integral squared error filters with an explicit control of the transition band edges. Design formulas for approximations to ideal frequency responses which use a pth-order spline transition function are derived and analyzed. A variable-order spline is used with a method for optimally choosing the order. The results of this method are compared with those of other optimal methods.<<ETX>>