Beam-steerable radial-line slot antenna array

The authors describe the design and performance of an annular slot planar array antenna which can steer right-hand or left-hand circularly linearly polarised waves. The array consists of a radial cavity waveguide whose elements, 12 crossed slots, are designed to radiate in the frequency range 9.1-9.4 GHz. Phase shifters are realised by positioning dielectric fins in circular waveguides above each of these slots. In addition, the use of a four-probe three-post polariser to feed the radial cavity permits LHCP, RHCP or LP to be generated. The resulting array has an impedance bandwidth of 2% for <1.2 VSWR. Beam scan angles of up to 35/spl deg/ for RHCP/LHCP and LP were measured at 9.2 GHz and the gain of the antenna was 12.8 dBi.