Linear phase digital filter design

The results of an investigation of linear phase digital filters are presented. It was determined that stable filters of this type are necessarily nonrecursive. The corresponding transfer function is presented in a general form in terms of basic z-plane pole and zero configurations. The design of digital filters of this form is accomplished by approximating a desired frequency function by one of four types of Fourier series. The types of series correspond to the forms of the z transfer function polynomial, which is either a mirror-image polynomial or a negative mirror-image polynomial, and either even or odd order.