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Abstract
In wireless communications utilizing high altitude platforms, the cellular coverage depends on the sidelobe level of the used antennas which affects the carrier-to-interference ratio (CIR). Many antenna configurations are applicable but antenna arrays are more flexible than spot-beam antennas. Therefore, this paper proposes a beamforming technique based on tapering the array feeding currents with a Gaussian function for sidelobe reduction. The antenna array configuration is chosen as the uniform concentric circular arrays (UCCA) and the simulations for a HAP cellular system consisting of 69 cells shows that the CIR may reach 43 dB at the cell center and about 20 dB at the cell edge for a typical cluster size of four. The innovated beamforming technique applied to UCCA is compared with other conventional array configurations such as square two-dimensional arrays (TDA) showing an increase of the CIR by 13 dB at the cell edges and about 26 dB at the cell center.