Novel modal transitions for leaky modes on microstrip lines

In this paper it is shown that a novel transition may occur for dominant leaky modes on microstrip line, between a leaky mode that leaks into the TM0 surface-wave and one that leaks both into the TM0 surface wave and into space. The evolution of these leaky modes is studied as a function of frequency by means of a full-wave spectral domain approach, and it is shown that such a transition may occur on microstrip lines that have a critical strip width, which is relatively large. The continuous-spectrum current excited by a finite source can be significantly enhanced when the frequency is near the transition frequency, resulting in very high spurious effects.