Given,
FT = 22.050kHz
fP = 500 Hz
fS = 400Hz
p = 0.02
s = 55dB
p=
= 0.045351473
= 0.036281179
= 0.0454
= 0.0363
Passband ripple, p
p = -20 log (1- p)
= -20 log (1-0.02)
= 0.175478486
= 0.1755 dB
Assume T=2;
p = tan (
= 0.07143
s = tan (
= 0.05705
Minimum order of FIR high-pass digital filter.
Known, s=55dB
The order of FIR high pass filter can be determined by using this table below:
Type of Window
Hann
Hamming
Blackman
Minimum Stopband
Attenuation
43.9dB
54.5dB
75.3dB
Transition Bandwidth, w
3.11/M
3.32/M
5.56/M
Table 1 : Window specifications table
From the table, the filter can be designed using Hann and Hamming as the minimum
stopband attenuation is lower than 55dB.
The order of Hann window :
w =
p-
= 0.0454-0.0363
= 9.1 x 10^-3 
From the table,
w = 3.11/M
M= 3.11/(9.1 x 10^-3 )
= 341.758
N = 2M + 1
=2(341.758) + 1
= 684.52
N = 685
The order of Hamming window :
From the table,
w = 3.32/M
M= 3.32/(9.1 x 10^-3 )
= 364.835
N = 2M + 1
=2(364.835) + 1
= 730.67
N = 731
The order of Kaiser window :
Known, s=55dB
N=
=
= 720.25
= 720