Finite Impulse Response Filters - Introduction to Digital Signal Processing and Filter Design - page 277

FIR LP filter response with N = 85 and Hamming window

20

0

− 20

− 40

− 60

− 80

− 100

− 120

0 0.1 0.2 0.3 0.4 0.5

Normalized frequency

0.6 0.7 0.8 0.9 1

Figure 5.13 Magnitude response of a FIR lowpass filter using Hamming window.

Magnified plot of the LP filter response

1.01

1

0.99

0.98

0.97

0.96

0.95

0.94

0 0.05 0.1 0.15

Normalized frequency

0.2 0.25 0.3

Figure 5.14 Magnified frequency response of a FIR lowpass filter in the passband.

until the specifications are met. For the lowpass FIR filter, we have had to choose
ω c = 0 . 35 and N = 65 so that at the frequency ω = 0 . 3, the error δ p ≤ 0 . 01 and

at ω ≤ 0 . 01 (equal to 40 dB). The magnitude response of this

final design is shown in Figures 5.13 and 5.14. Similar changes in the design of
the other filters designed by the Fourier series method are necessary.

= 0 . 4, the error δ s