Improved Modelling of Tapered IDG Antennas

The currents fowing on the finite ground plane of the inset dielectric guide tapered slot antenna (IDG-TSA) have a significant effect on the radiation characteristics of the structure. The most complete analytical model of the IDG-TSA that has been developed to date [1] uses empirical methods to establish the magnitude of the ground plane currents. We present here a new method which locks the ground plane currents to those on the slot surface by applying static field theory in the vicinity of the slot edge. In this paper, measured results are presented for a long horizontally polarised antenna, as well as for novel short structures of both polarisations. Good agreement is shown between measured values and predictions made using the new theoretical technique, and the results show an improvement on those obtained by previous methods. The measured data indicates that the short antennas may be suitable for use as elements in phased arrays. Further, by comparison of measured data to the results of finite-difference time-domain simulations, we show that the effect of the finite ground plane is extremely important in determining the radiation characteristics of the vertically polarised IDG-TSA.