An Experimental Investigation of the Dielectric Rod Antenna of Circular Cross Section Excited in the Dominant Mode

Abstract

The radiation pattern and the gain were measured for four series of dielectric antennas of circular cross section. These antennas were excited by a TE11 mode in a circular metallic wave guide at a frequency of 9275 mcps. Only one parameter was changed in each series of rods so that the effect of this parameter on the pattern and gain could be studied. Measurements of gain are presented for two further series of rods in which the length is varied. The measurements showed that a polystyrene rod of length 6λ0 and constant cross section has maximum gain and best pattern for a diameter of approximately 2λ0. On the other hand when the taper of a Lucite rod was varied while the length and the maximum diameter were held constant at 6λ0 and 0.87λ0, respectively, the gain and the pattern behavior improved as the minimum diameter was decreased to zero. It is shown that losses in the dielectric produce a significant decrease in the gain.