2. Windows
• Windows are the finite duration sequences used to modify
the impulse response of filters in order to reduce ripples in
passband and stopband and to achieve desired transition
from passband to stopband.
• The infinite duration impulse response can be converted to a
finite duration impulse response by truncating the infinite
series.
3. But this results in undesirable oscillations in the passband and
stopband of digital filter which is due to the slow convergence of
Fourier series near the points of discontinuity.
These undesirable oscillations can be reduced by using a set of
time-limited weighting functions, w(n), referred to as window
functions , to modify fourier coefficients
12. Q. Design a LPF using hamming window to
meet following specifications
4
||0.............{)( 2
j
d eH
nfor.......
n..........
)(
))(sin(
)(
c
for
n
n
nh c
d
Solution :
2
1
M