In this experiment, we designed a linear phase FIR filter - low pass and band pass. We plotted the magnitude and phase plot of both the filters. In this method, the desired impulse response is multiplied with window function w(n) to obtain h(n) which after Z-transfrom yields the transfer function H(z).
The Input specifications are Pass band frequency,Stop band frequency, Pass band attenuation, Stop band attenuation, Sampling frequency. Selection of window depends on Stop band attenuation in dB.The window function i used was Hamming window.The phase plot being linear, there will be no distortion at the output. We later also observed attenuation in stop band is maximum for Blackman window and minimum for Rectangular window.
As we go on increasing As, depending upon filter, side lobe width decreases with increasing main lobe width.
We faced some difficulty in getting the coefficients and phase plot in the same scilab code so we wrote the c code for getting the h(n) coefficients and using these coefficients we plotted the phase plot in a separate scilab program. Term tests were on the line. Even last moment assignments caused us a delay.
As we go on increasing As, depending upon filter, side lobe width decreases with increasing main lobe width.
We faced some difficulty in getting the coefficients and phase plot in the same scilab code so we wrote the c code for getting the h(n) coefficients and using these coefficients we plotted the phase plot in a separate scilab program. Term tests were on the line. Even last moment assignments caused us a delay.
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ReplyDeleteso is blackman window best for filter design
ReplyDeleteYes though it is better the computational effort required is more. The selection of a specific window depends on your own specifications of stop band attenuation that is specified by the user.
Deleteyup thats what we observed
ReplyDeleteBecause attenuation in stopband is most for blackman window function
ReplyDeleteAs of window function should be higher than that of filter.
ReplyDeleteRectangular window is rarely used for truncation as As is very low as compared to other window functions.
ReplyDeleteAs of rectangular function is only 21
ReplyDeleteThe window method is based on calculating the impulse response of an ideal digital filter, which is IIR, and on using a window to obtain a finite impulse response. The characteristics of the FIR filter depends on the chosen window. One of the most interesting properties you can get is linear phase.
ReplyDeletethank you for giving value by using rectangular window
ReplyDelete