Effects of slot dimensions and operating frequencies on the equivalent magnetic current distributions in slot antennas

The objective of this paper is to investigate effects of the slot dimensions and operating frequencies on the equivalent surface magnetic current distribution in slot antennas. For this purpose, field equivalence principle applied with appropriate boundary conditions enables derivation of model equation of the magnetic current in the slot. Solution of the derived integro-differential equation using the method of moments as a numerical tool yields the needed magnetic current distribution in the slot. It is shown here that the magnetic current distribution of a half-wave slot is bell-shaped and tapers to zero at both ends of the slot length at all frequencies while those of fixed length slots have different profiles at different frequencies. Besides, magnetic current distributions of fixed length slots do not taper to zero at slot ends. It is also established here that the absolute value of magnetic current density of half-wave slot increases linearly with frequency whereas that of fixed length slot does not follow a definite pattern. Those behaviours of slots indicate that fixed length slots perform better at certain frequencies than others, while half-wave slot presents an idealized situation. Two validations of the present formulation which are reported in this paper border on the consistency of the vanishing tangential component of the electric field on conductor as well as the well-known bell-shaped current characteristics of dipoles which are duals of slots.