WINDOWING TECHNIQUES OF FIR FILTER DESIGN
Presented by,Soumil Agarwal (J001), Aayush Maheshwari (J015), Rohan Nagpal (J019), Vibhuti
Maheshwari (J036)
WHAT IS A WINDOWING?
A window is a finite length sequence.
Windowing is a process of forming a finite length sequence from an infinite length sequence by multiplying an infinite length sequence with a window.
GENERAL PROCEDURE FOR WINDOWING1. Choose the desired frequency response of the filter Hd (ω)
2. Take inverse fourier transform of Hd (ω) to obtain the desired impulse response hd (n)
3. Choose a window sequence W(n) and multiply hd (n) by Hd (n) to convert IIR to FIR h(n)=W(n) x hd (n)
4. Taking ZT of h(n) we obtain a transfer function H(z)
5. Realize the filter using suitable filter method
TYPES OF WINDOWS
WINDOWS
Rectangular Hanning Hamming Blackman Bartlett
Depending on the stop band attenuation we will select a window. Stop band attenuation (As) are the lower limits of attenuation.For example, if As is 40 dB, we will choose Hanning Window
WINDOW EQUATIONS
EXAMPLE
STEP 1- CHOOSE THE DESIRED FREQUENCY
STEP 2 – TO FIND Hd (n)
STEP 3 – CONVERSION OF FINITE TO INFINITE SERIES
STEP 4– TO FIND H(z)
STEP 5 - LINEAR PHASE REALISATION
ADVANTAGES AND DISADVANTAGES Simple – involves minimum computation Maximum ripple amplitude in filter response is fixed regardless of
how large the filter order is
Lack of flexibility When the expression for the desired filter response Hd(e^jw) is
complicated or cannot be put into a closed form mathematical expression, evaluation of Hd(n) becomes difficult.
THANK YOU
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