Investigation of Behaviours of Kerwin-Huelsman-Newcomb Filters Using Nichols Charts of Self-Loop Function

In this paper, an investigation of the operating regions of the Kerwin-Huelsman-Newcomb filters based on the characteristics of Nichols charts is presented. In recent research papers, the idea of loop gain cannot be used in many feedback systems because the mathematical relationships between loop gain and closed-loop gain do not exist. Moreover, both Nyquist and Nichols charts of loop gain do not describe three different behaviors of high-order networks. Furthermore, the Kerwin-Huelsman-Newcomb topology is one of the most important filters in modern telecommunication systems while the behaviors of phase margin in this architecture are not well analyzed. Hence, the ringing test for three different cases of the second-order Kerwin-Huelsman-Newcomb filters is proposed and described in detail. The experimental measurements of the phase margins are 50 degrees (under-damping region), 77 degrees (critical damping region), and 83 degrees (over-damping region). It shows that the ringing test has a very clear electronic technical meaning and reflects the important role of the Nichols chart in the high-order networks.