An efficient analysis of radiation from slotted coaxial cable using the spheroidal wave function

An efficient modal-expansion analysis is developed for obtaining the current distribution of a slotted coaxial line antenna with a length up to 10 lambda. In our analysis, the outer conducting body of a long and thin coaxial line is approximated into the thin prolate spheroidal, and the corresponding wave functions are used to express the electromagnetic fields outside the coaxial line. Matching the outer and inner electromagnetic fields over the slots on the surface of the coaxial line, the current distribution can be efficiently solved. Reasonable accuracy is obtained when results of this method are compared with those available in the literature. (C) 1999 John Wiley & Sons, Inc.