A new approach to antenna beam-shaping - The "Coke-bottle" antenna

The theoretical development of a new method of vertical plane-beam-shaping from Wullenweber three dimensional arrays is presented along with a particular design formulated by the theoretical techniques. The method essentially consists of expanding the desired pattern in a Fourier series expansion and relating the parameters in the expansion to the parameters in the Wullenweber array. Three parameters are allowed to vary: (1) The interelement spacing (2) The diameter of the Wullenweber at each element, and (3) The amplitude or current distribution along the array. These three variables are sufficient to produce any arbitrarily shaped antenna pattern with a least-squares approximation. The antenna is basically a Wullenweber array but it is particularly unique in that the diameter of the Wullenweber changes with height so that it has a characteristic "Coke-Bottle" shape. The space-phasing due to the particular shape plus the amplitude taper of the elements in the vertical plane results in an asymetrical, truncated, cosecant-squared elevation pattern from the uniformly phased array. The wide band operation of the array is demonstrated through patterns made on a scale model array over a two-to-one frequency band.