Simulation of nonlinear baseband device with higher-order transient characteristics via a second order nonlinear recursive filter

It is shown that, when approximating the order of transient responses of baseband devices, the initial segment of the rising edge has the dominant influence. For the digitization device under test, the transient response exhibits an order higher than two. Although this effect is negligible in simulation, it significantly impacts the accuracy of measuring the model’s characteristic functions. A method is proposed in which higher-order transient responses are satisfactorily approximated by the response of a second-order nonlinear recursive filter through the addition of a Gaussian linear filter. The influence of placing the Gaussian filter either at the input or at the output of the nonlinear recursive filter on the characterization quality is analyzed. It is shown that applying the Gaussian filter at the input reduces the error in determining the characteristic functions (the charge–volt and magnetic flux–current characteristics) from 28 % to 1 %, while the accuracy of transient-response modeling relative to measurements reaches 3 %, which overall represents a satisfactory result.