Design of narrowband frequency sampling FIR filters using Z-window

In this work a method for automatic design of narrowband frequency sampling low-pass digital FIR filters is presented. Spectral response of Zhong (Z)-window has been used to provide the filtering action. Z-windows are used as variable windows by varying the side-lobe dip position. The proposed design methodology is a hybridization of the concepts of frequency sampling method and window method of filter design. This proposed design technique produces low-pass FIR filters featuring sharp cut off, exactly marked pass-band and cut off frequencies along with tolerable pass-band ripple and variable stop-band attenuation. For the filter applications requiring “brick–wall” response, considerable saving in the filter order can be achieved with subsequent reduction in computational and storage requirements by this method.