Circularly polarized multimode smart antenna system for micro base station application

A smart antenna system suitable for micro base stations is proposed, which consists of three left-handed circularly polarized designs operating at 3.5 GHz. The first one is an eight-port cylindrical conformal antenna with both omnidirectional and directional modes. Its maximum omnidirectional realized gain is 5.0 dBic, and its maximum single/dual beam realized gain under the directional mode on the horizontal plane is 9.4/6.9 dBic. In addition, it can achieve elevational scan from 70 degrees to 110 degrees. The second one is based on the first one with a feeding network, therefore reducing the number of ports to four, achieving a maximum omnidirectional and directional realized gain of 4.2 and 7.9 dBic. The third one is also based on the first one, but with two additional omnidirectional antennas added, making it a hybrid system with enhanced omnidirectional radiation. It has a maximum omnidirectional and directional realized gain of 6.4 and 8.2 dBic. To validate the proposed concept, three prototype arrays are designed, fabricated, and measured, showing that the proposed antenna system can achieve the desired radiation patterns according to different targeted applications.