Polarisation diversity microstrip base station antenna at 2GHz 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 50dB 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 15dB return loss bandwidth, the measured S₁₁ is 24.8% (1.746-2.24GHz) while S₂₂ is 20.5% (1.775-2.18GHz), respectively. These results are in good agreement with those obtained using simulation. The measured isolation is between 25 and 40dB, and the antenna gain is 13 ± 0.5dBi over the required frequency range.