A planar omnidirectional antenna with dual polarizations for base station applications

Abstract

A new planar omnidirectional antenna with vertical polarization (VP) and horizontal polarization (HP) suitable for base stations is presented and discussed. The proposed antenna is a collinear printed structure, which is designed using the combination of folded microstrip patch array for VP and the modified slot array loaded by metal sheets for HP. This omnidirectional antenna has the advantages of simple structure, low profile, low cost and dual polarizations. An antenna prototype for demonstration is fabricated on a FR4 board with the size of 30 mm (width) × 350 mm (length) × 26 mm (height). The measured 10-dB impedance bandwidths for VP and HP are 445 MHz (2.4–2.845 GHz) and 230 MHz (2.51–2.74 GHz) respectively. The measured gain variation of less than 4 and 2.6 dB in the horizontal plane can be obtained for VP and HP at 2.5 GHz. The measured isolation between the two feeding ports for VP and HP is better than 40 dB over the whole bandwidth. Good agreement between the measured and simulated results can be observed.

Keywords:

• Omnidirectional
• dual polarizations
• collinear
• folded microstrip patch
• slot