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

FIR Filters 18-29selective step-by-step search in conjunction with the cubic-interpolation search reduced the amount ofcomputation by about 83.7%, relative to that required by the exhaustive search.The three methods resulted in approximately the same impulse responses, as can be seen in Table 18.6.The amplitude response of the filter is illustrated in Figure 18.18; the passband ripples obtained for the twopassbands were 1.78 and 0.89 dB, respectively, and the minimum stopband attenuation was 33.79 dB.Gain (dB)50–5–10–15–20–25–30–35–40–45–50–55Amplitude response(a) 01 2 3Frequency (rad/s)1Amplitude responseGain (dB)0(b)–1010.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8Frequency (rad/s)Amplitude responseGain (dB)(c)–1Frequency (rad/s)3FIGURE 18.18 Amplitude response of equiripple bandstop filter (Example 18.2): (a) baseband, (b) lower passband,and (c) upper passband.