The design of linear phase FIR filters using the IDFT

The paper presents a comprehensive set of equations for specifying the transfer function of linear phase finite-impulse response (LPFIR) filters. A procedure for designing the eight possible LPFIR filters (symmetric and anti-symmetric, even and odd length, type 1 and type 2 filters), using the inverse discrete Fourier transform (IDFT) is described. This technique can be equally applied to the window method and the frequency sampling method.