Spectral domain analysis of electrically wide short-circuit discontinuities in slotline

Rigorous spectral-domain analysis of uniform slotline has shown that the longitudinal electric field can be significant in electrically wide slots and in slots on electrically thick substrates. The present study includes the effects of both longitudinal and transverse electric slot fields and incorporates the proper edge conditions for each component of the field at the edges of the slot and the short-circuited end of the slot. Like the open-circuit discontinuity in microstrip, the short-circuit slotline discontinuity is nonideal because it radiates power into surface and space waves. The nonideal aspects of open-circuit microstrip and short-circuit slotline discontinuities are compared. The magnitude and phase of the reflection coefficient versus frequency are plotted for a shorted slotline on a substrate with a relative dielectric constant of 20.0 and thickness of 3.175 mm for various slot widths. It can be seen that, as with the microstrip open-circuit discontinuity, the radiation loss becomes very large near the cutoff frequency of the second surface wave mode.<>