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低通 Bessel 滤波器的频率响应

设计一个五阶模拟低通 Bessel 滤波器,其群延迟在频率达到 104 弧度/秒前大致恒定。使用 freqs 绘制滤波器的幅值和相位响应。

[b,a] = besself(5,10000);
freqs(b,a)

Figure contains 2 axes. Axes 1 contains an object of type line. Axes 2 contains an object of type line.

计算未展开相位响应的导数以得到滤波器的群延迟响应。绘制群延迟,以验证它在不超过截止频率前大致恒定。

[h,w] = freqs(b,a,1000);
grpdel = diff(unwrap(angle(h)))./diff(w);

clf
semilogx(w(2:end),grpdel)
xlabel('Frequency (rad/s)')
ylabel('Group delay (s)')

Figure contains an axes. The axes contains an object of type line.

另请参阅

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