A wideband circularly polarized antenna with pattern improvement

A novel wideband circularly polarized (CP) microstrip antenna with pattern improvement is proposed. Four vertical conductive walls surrounded with the radiation patch and four metal isosceles triangle patches located at top of the radiation patch are employed for widening beamwidth. To achieve the miniaturization of the antenna, four slots etched along the diagonals of radiation patch and the folded ground plane structure are used due to extending the current path. In addition, by introducing an electromagnetically coupled method and a compact broadband phase shifting network, the antenna achieves a wide impedance bandwidth for VSWR≤1.5 ranging from 1.1 to 1.72 GHz and a 3-dB AR bandwidth from 1.1 to 1.7 GHz.

I. Introduction

Circularly polarized (CP) antennas are receiving much more attention nowadays, owing to their importance in various wireless systems such as mobile communication systems, radar, radio frequency identification (RFID), senor systems, and Global Navigation Satellite System (GNSS). Circular polarization, compared to linear polarization, allows for better flexibility in orientation angle between transmitter and receiver, better mobility, weather penetration, and reduction in multi-path reflections or other kinds of interferences. With these advantages, circularly polarized antennas are widely employed in various wireless systems