High efficiency hexagonal short backfire antenna with hard walls for GPS satellite antennas

Short Backfire Antennas (SBFAs), first published in 1965 (H. W. Ehrenspeck, “The Short Backfire Antenna,” Proc. IEEE, Vol. 53, No. 8, pp. 1138–1140, Aug. 1965), have seen wide use in terrestrial, maritime and space-based applications due to their relatively high directivity and low profile. Typical SBFA height is 1/8 that of comparable end-fire elements like the Yagi for the same nominal 15 dBi directivity, and typical SBFA aperture diameter is on the order of 2λ. Achievable SBFA aperture efficiency is 84% at a single frequency, and about 75% average for a dual-band application like that of the L1 (1.575 GHz) and L2 (1.227 GHz) GPS frequencies. In an array application, an additional 10% aperture efficiency loss will occur due to packaging of circular SBFA elements, bringing the overall GPS L-band array aperture efficiency down to 67%.