In this experiment we designed a FIR filter with the help of windowing method. A window function is basically used to truncate the infinite values obtained after the IDTFT operation on the phase response function. A suitable window function is selected depending upon the stop band attenuation which is an input specification.. The output response was observed in the form of a graph on the scilab software and results was verified.
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ReplyDeleteRectangular window function should be avoided due to low value of stop band attenuation.
ReplyDeleteYes in case of rectangular window the value of As is 21 dB , so if one requires a higher attenuation for design purpose (which generally is requirement) , the output won't be what we expect.
DeleteAttenuation of the side lobes is an important factor.
ReplyDeleteYes and a window with higher stopband attenution will fetch you with desired results.
DeleteBlackman window function is considered as the best window function as it has the highest stopband attenuation
ReplyDeleteStopband attenuation (As) decides selection of Window function.
ReplyDeleteSelect your window such that its value of stop band attenuation is just above your required value of the same. For example if your required value of As is 42 dB, select Hanning window with stop band attenuation 44 dB
DeleteHanning too gives a good response
ReplyDeleteThe trick is to select the window function that will give a filter with the correct transition width and attenuation in stopband.
ReplyDeleteStop Band value(As) of the windowing function must be high
ReplyDeleteWindow function is selected on the basis of As value
ReplyDelete