Polarisation diversity microstrip base station antenna at 2 GHz using T-shaped aperture-coupled feeds

A prototype 1×4 microstrip array antenna for the IMT-2000 base station using +/-45° slanted polarisation diversity is proposed to overcome the problems of space diversity. ´T´ shaped aperture coupled feeds are used to obtain good isolation. For a single radiating element, isolation of up to 50 dB between the two ports has been obtained. Stacked patches are also used for broadband operation. For the 1×4 array, the distance between each radiating element is 0.92λ₀ and a corporate feed is used. The overall size of the array antenna is ~160×500×40mm. Based on 15 dB return loss bandwidth, the measured S₁₁ is 24.8% (1.746-2.24 GHz) while S ₂₂ is 20.5% (1.775-2.18 GHz), respectively. These results are in good agreement with those obtained using simulation. The measured isolation is between 25 and 40 dB, and the antenna gain is 13 ± 0.5 dBi over the required frequency range