Factors governing the radiation characteristics of dielectric tube aerials

As very little published work on dielectric tube aerials is to be found in the literature, the paper is intended to dis cuss the fundamental principles governing the radiation patterns of dielectric tubes rather than to present a detailed study of one or more aspects of the subject. The influences of the tube length, diameter and wall thickness on the radiation pattern were investigated experimentally and an approximate theory is presented which is in agreement with the experimental results. From this investigation it is suggested that the mechanism of radiation of dielectric tubes having thin walls more closely resembles that of a lens or corrective re-radiator than that of a leaking waveguide system, such as a dielectric rod aerial. Thus it is concluded that the dielectric tube and rod, though similar in many respects, are fundamentally different types of aerials.