Radiation from ring quasi-arrays

The present paper constitutes a summary of investigations of certain antenna systems with rotational symmetry, so-called ring arrays and ring quasi-arrays, which have turned out to be or can be supposed to become of practical importance. Particular stress has been laid on an investigation of the field radiated from homogenous ring arrays of axial dipoles and homogeneous ring quasi-arrays of tangential and radial dipoles; i.e., systems of respectively axial, tangential, and radial dipoles placed equidistantly along a circle and carrying currents of the same numerical value but with a phase that increases uniformly along the circle. At first a calculation has been made of the radiated field in the case where the number of elements in the antenna system is infinitely large. After that the influence of the finite number of elements is accounted for by the introduction of correction terms. Subsequently, the radiation resistance and the gain have been calculated in a few simple cases. The antenna systems described above may display super-gain. On the basis of the theory of super-gain an estimate is made of the smallest permissible radius of these antenna systems. Further an investigation is made of the field from a directional ring array with a finite number of elements to ascertain in particular the influence on the field of the finite number of elements.