Broadband Circularly Polarized Antenna Design and Simulation for 5G IoT Applications

In order to realize applications of communication systems in different frequency bands, such as GNSS receivers, Bluetooth, RFID systems, WLAN applications, wide-band antennas are needed. In this paper, a broadband circularly polarized antenna is designed for 5G IoT applications at ISM band. The dimension of the antenna is $80\times 80\times 8.5\ \text{mm}^{3}$. At the top of antenna, rectangular patch is printed on FR4 substrate of thickness 1.5 mm with 4.4 of relative permittivity. At the backplane of the lower F4B substrate of thickness 2 mm with 2.65 of relative permittivity there is a feeding network based on high directivity microstrip directional coupler. Between the two substrates is filled with air of thickness 5 mm with 1 of dielectric constant. The antenna is designed by using HFSS software, the simulated antenna at 2.45GHz frequency offers wide impedance bandwidth $(\mathrm{S}_{11} < -10\ \text{dB})$ of ~640MHz (2.2 – 2.84 GHz) and 3 dB axial ratio bandwidth of ~500MHz (2.3 – 2.8 GHz), shows good performance in terms of gain and S-parameters.