Dual polarized smart antenna beams

Interest has centered on the use of "smart antennas" in cellular as well as DCS 1800/PCS 1900 bands with a view to obtaining significantly improved spectral efficiencies, better quality of service, higher capacities, and improved coverage, while at the same time achieving significant savings in base station costs. The smart antenna directs its main lobe with the enhanced gain towards the preferred user, with the side lobes being directed towards the interfering users, thereby improving the C/I ratio. While typically adaptive arrays use space diversity in combination with an appropriate beamforming algorithm, in this paper we propose the use of an omnidirectional antenna in a polarization diversity scheme to provide enhanced performance at the base station. Beamforming is performed using a conjugate gradient algorithm which has been shown to provide rapid convergence in adaptive filtering applications, with moderate computational requirements. Simulation results are presented to illustrate the applicability of the method.