Circularly polarized multibeam radial line slot antennas for mobile satellite communication

Circularly polarized conical beam antennas have previously been investigated for the applications of the low G/T mobile satellite communication and broadcasting services (James and Hall, 1989). Takada et al. (1994) presented the design of a circularly polarized conical beam radial line slot antenna (CB-RLSA). The conical beam radiation is verified numerically and experimentally. However,the original design is not suitable for the application of a wider coverage angle (eg. /spl Theta/=10/spl deg//spl sim/70/spl deg/) or the higher gain (e.g. >7 dBi). The present paper proposes two types of multibeam RLSA. In both structures, only the feed circuit is modified to realize the multibeam operation. These feed circuits utilize the cavity type rotational mode generator (Hosono et al., 1994). One antenna radiates conical beams with different elevation angles for wider coverage angle. The other radiates azimuthally directed beams for higher gain. The numerical results for directive gain are presented.