Design method of fir digital filters with specified group delay errors using successive projection

This paper presents a design method of FIR. digital filters that meet simultaneously magnitude and group delay specifications using a successive projection method. Generally, the design Problem of FIR digital filters with low group delay is expressed as the minimization problem of the complex magnitude error, which includes the magnitude and phase information, and it is minimized instead of the group delay error. Therefore, the group delay characteristics of the filter obtained by solving such a design problem,may be distant from the desired group delay. In the proposed method, we define separately the approximation problems of the magnitude and the group delay characteristics, and these two approximation problems are solved alternately using successive projection. method. As a result, the proposed method allows the direct approximation of the group delay characteristics, and it can also restrict the group delay characteristics within the preselected allowable errors. The usefulness of the proposed method is verified through some design examples.