Antenna Arrays around Cylinders

Abstract

Arrays of dipoles around spires or other vertical supports are useful for the broadcasting of ultra-high-frequency waves. To the author's knowledge no sound method of computing the radiation patterns which takes into account the effect of the support has previously been presented. The three arrangements of dipoles around a vertical cylinder which are of interest are (1) an array of vertical dipoles, (2) an array of horizontal dipoles whose axes lie on the circumference of a circle, and (3) an array of horizontal dipoles whose axes point radially outward. There are several phase relationships for the currents which are of practical interest for each of these arrays. The necessary number of dipoles in various types of arrays to obtain a horizontal radiation pattern approaching a circle within any specified tolerance are shown by curves. The interference phenomena caused by a plane wave passing a vertical cylinder are discussed and shown graphically. Several radiation patterns for one dipole near a cylinder are discussed. A detailed study of a 4-element horizontal dipole array surrounding a cylinder whose diameter is 1.27 wavelengths, or whose periphery approximates that of the Chrysler Building spire at the assigned television frequency, has been made. Both horizontal and vertical patterns for three different phase relationships of the dipole currents have been calculated. Formulas for the radiation patterns for arrays of all three types having various numbers of elements and fed in several different ways are tabulated.