Variable radiation pattern of helix antennas

Two-wire or four-wire helical antennas, which are rod-shaped and space-saving and hence simple in structure, have been attracting attention as antennas to be used for mobile satellite communication base stations. Kawakami et al. (1997) reported that changing the phase shift and the number of turns of wire in the central portion enables vertical pattern fan beams to be formed which give desired gains. The present paper reports the results of consideration of the basic characteristics of two types of directivity, one which forms an enclosing shape and the other which forms a shoulder riding shape. Characteristics exhibited when a load is mounted on the portion where the antenna elements are placed are examined.