Low-Pass Filters Approximating-in Modulus and Phase-the Exponential Function

The family of low-pass filters under investigation in this paper possesses both the time-delay properties of Bessel filters and the attenuation properties of Butterworth filters owing to the fact that the transfer function employed approximates, in modulus and phase, the exponential function around the frequency origin. Moreover, the step response of these filters has a low rise-time. Examples are given pointing out the properties of this family of low-pass filters which appear to be suited for delay lines.