Passive, active, and digital filters (3ed., CRC, 2009) - tiera.ru

FIR Filters 18-130–20Amplitude response (dB)–40–60–80–100–120 0 0.5 1 1.5 2 2.5 3 3.5Frequency (rad)FIGURE 18.11Magnitude response of low-pass FIR filter design using a 31-point Hamming window.0–20–40Amplitude spectrum (dB)–60–80–100–120–140–160–180 0 0.5 1 1.5 2 2.5 3 3.5Frequency (rad)FIGURE 18.12Fourier transform of the Blackman window.The amplitude response of the Blackman window is shown in Figure 18.12. It can be seen that it has thehighest sidelobe level, down 57 dB from the mainlobe peak. However, the mainlobe width has increasedto 12p=N.The amplitude response of the FIR low-pass filter obtained when applying the Blackman window is shownin Figure 18.13. The minimum attenuation in the stopband is about 74 dB, but it occurs for v > p=2.The Kaiser window. For the foregoing windows, the width of the mainlobe is inversely proportional to N.However, the minimum stopband attenuation is independent of the window length and is a function of