Design of a small and low-profile 2/spl times/2 hemispherical helical antenna array for mobile satellite communications

A small and low-profile 2/spl times/2 hemispherical helical antenna array was designed for INMARSAT satellite reception. With only four elements fed by a simple network, the array can produce a gain of 15 dB, a 3-dB axial ratio bandwidth of nearly 14%, a cross-polarization level of smaller than -20 dB over the half-power beamwidth, and a radiation pattern with a sidelobe level of -20 dB. These characteristics are better than those obtained by previously proposed INMARSAT-M antennas.