Circularly Polarized Square Patch Array Antenna with Multiple Rectangular-Slots Fed by Proximity Coupling Technique

This paper deals with the development of circularly polarized square patch array antenna for 5GHz wireless local area network (WLAN) application. One of essential benefits applying circularly polarized array antenna is the capability in minimizing the Faraday effect. The proposed array antenna consists of 5 microstrip square patch elements designed on 2 layers of FR4 dielectric substrate with 0.8mm thick of each layer. Each square patch element with multiple rectangular-slots to achieve circular polarization is fed by using proximity coupling technique to improve the radiation characteristics. Some investigations upon the geometry of array antenna as well as its feeding lines are carried out through simulation to gain an optimum architecture design implemented for hardware realization. The characterization results show the realized array antenna with the dimension of 119mm $\times$ 44.1mm could achieve the gain more than 6dBi around the frequency of 5GHz with the 3dB axial ratio bandwidth of 262MHz.