A Least Mean Square Based Method of Lowpass Fir Filter Design Using the MATLAB Toolbox

Abstract

A lowpass digital filter was designed using the MATLAB toolbox. The programme code was based on the least mean square error criterion method and was run in two steps – viz- filter order estimation from given specifications, and determination of the coefficients of the transfer function using the estimated order and filter specifications. The amplitude response of the linear phase FIR filter was used to obtain a realizable filter transfer function for filter length, N = 40. It was observed that for a longer length the FIR filter has a sharper cut off FIR filter and a narrow transition band. This makes it suitable for processing baseband signals especially digitized voice, music and data signals. All tests were carried out with the aid of the command window, which was unlocked from the workspace desktop for easy accessibility.