Polystyrene Rods Research Articles

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

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.

On the Directional Patterns of Polystyrene Rod Antennas

Experimental and theoretical directional patterns are compared for three polystyrene rod antennas of length variable from about 4 to 10 wavelengths, retaining relative shape in the length direction. The comparison shows that the apparent index of refraction, n, decreases with increasing length. Accordingly, the directional patterns are less sharp than might be expected from the estimated values of n which are constant for a constant relative shape.

An Investigation of Dielectric Rod as Wave Guide

An experimental investigation of dielectric rod as wave guide indicates that the guiding effect is retained even when the rod is only a fraction of a wave-length in diameter. The greater part of the guided energy is then outside the dielectric, so that a very low loss wave guide results. Measurements of performance made at 1.25 cm indicate attenuations down to 0.004 decibel per meter in polystyrene rod, and show good agreement with theoretical predictions. A resonator utilizing the dielectric-rod wave guide is described, in which a maximum Q of approximately 53,000 was observed.

The Radiation Patterns of Dielectric Rods—Experiment and Theory

A theory is developed describing the electromagnetic radiation from dielectric rods used as terminations to rectangular wave guides. The radiation patterns are computed from the fields due to equivalent magnetic and electric currents on the surfaces of the rods. These equivalent currents are determined by use of Schelkunoff's equivalence principle applied to approximate fields within the dielectric. Specific calculations are carried out for rods whose average dimensions are 0.9″×0.25″ and whose lengths vary from three to ten wave-lengths. Experimental patterns are obtained for eight polystyrene rods, some of which are variable in length. Agreement with theory is found for rods from three to six wave-lengths long; differences between experiment and theory are discussed.