An accurate gate delay model for high speed digital and analog circuits

At present, most of simulation programs can characterize gate delays of microwave transistors. However, the delay is mostly approximated by means of a first-order differential equation only. In the paper, a more accurate way is suggested which is based on an appropriate second-order Bessel function. The delay model is implemented to a slightly but efficiently modified classic MESFET model. The proposed model does not create spurious oscillations that are typical for any LC approximations, and the simulation times are comparable with those obtained without the delay model. Properties of the implementation of the second-order Bessel function are demonstrated by an analysis of a tunable distributed microwave oscillator.