High-Frequency Pulse Distortion on a Lossy Microstrip Line With a Top Cover

This paper studies the time-domain propagation and dispersion of a pulse propagating on a microstrip line with a metallic top cover. A gap voltage source is used to model a practical excitation on the line. High-frequency distortion effects are observed that cannot be accounted for by conventional transmission-line theory, since they are due to the simultaneous excitation of the bound mode and a strong leaky mode. The bound-mode and leaky-mode components of the pulse are identified and separately studied to aid in the physical interpretation of the pulse distortion. The excitation of a dominant leaky mode gives rise to an interesting pulse-splitting phenomenon, due to the different velocities of the bound mode and the leaky mode. The influence of dielectric and conductor losses on the pulse shape is also studied.