A BICONICAL MULTIBEAM ANTENNA FOR SPACE-DIVISION MULTIPLE-ACCESS

The biconical antenna is well known as an easy to build broad-band ant enna with omnidirectional radiation. In this paper, the biconical ante nna is modified for selective radiation in azimuth direction. By enlar ging the diameter of the coaxial feed to the biconical antenna, a set of higher order modes can be excited. In addition to the angular indep endent TEM mode, higher order TE-modes are also allowed for propagatio n, which result in an angular dependent far-field pattern. Several fea tures of this multimode excitation are of interest. Applying multiple input feed connectors allows simple rotation of the antenna beam by sw itching or, when independently operated, transmission and reception fo r communication in different angular directions for real-time space di vision multiple access (SDMA). As with conventional antenna arrays, ad aptive pattern synthesis can also be realized by using multiple input feed connectors in combination with an appropriate amplitude and phase shifting network, The antenna allows an extremely flexible design of its characteristics at low cost, both requisites for SDMA communicatio n.