Step Response: Sketch the step responses of these fourth-order low-pass filters with 3-dB cutoff frequency of 1 kHz: Butterworth, Chebyshev, and Bessel.

Answer: Although the Butterworth has a maximally flat frequency response, the same cannot be said for its step response. As you can below, the Butterworth step response overshoots, then undershoots, then rings for a while around its final level. In some applications this is not acceptable.

The step response of the Chebyshev is even worse as you can see below.

The reason for using a Bessel filter in some applications is because of its outstanding step response shown below. As you can see, it has virtually no overshoot or ringing. This kind of response is very important in data communications because digital signals consist of positive and negative steps.

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