DIPOLE EXCITED UNIDIRECTIONALLY CONDUCTING SPHERE.
WASHINGTON UNIV SEATTLE COLL OF ENGINEERING
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The problem of frequency independent antennas has aroused the interest of many authors in recent years. In this work an attempt is made to solve the problem of a unidirectionally conducting sphere excited by a radial point source. As it is well known, a unidirectionally conducting surface constitutes, under certain restrictions, a good approximation to a surface consisting of many closely spaced conductors by choosing the direction of conduction on the sphere to be an equiangular spiral, an approximate mathematical expression was obtained for the fields produced by a spherical spiral antenna. This antenna exhibits certain broad band characteristics all of which are kept by the unidirectionally conducting surface. A study of this surface revealed considerable physical insight on the behavior of the spiral antenna. The problem is formulated in terms of vector potentials and solved by the method of characteristic Greens functions. The complexity of the formal solution necessitates approximations which lead to asymptotic estimates of the far zone radiation field.