Broadband CPW-Fed Circularly-Polarized Antenna for Sub-GHz IoT Applications

A novel design of a Coplanar Waveguide (CPW) fed antenna is proposed and fabricated for circularly polarized (CP) radiation. This broadband antenna is designed for long range and low power consumption within sub-1 GHz IoT applications. The proposed antenna is optimized to operate in sub-1 GHz bands using a CPW-fed with F-shaped feeding line. To obtain circular polarization, the patch antenna is truncated by a square of 20mmX20mm at the four corners and inverted L-shaped strips are attached to the ground plane at the opposite corners. Additionally, a metallic strip is introduced from the lower corners of the patch and extends into the center of the slot. A prototype of the antenna is fabricated and measured to verify the performance of this design. The measured -10 dB impedance bandwidth (IBW) and a simulated 3 dB Axial Ratio Bandwidth (ARBW) of the designed antenna were observed to be 107 MHz (893–1000 MHz) and 87 MHz (871–958 MHz), respectively. The simulated realized gain is 3.9 dB at 800 MHz and 3.7 dB at 1 GHz. In addition, the results of the simulation compared with the measured results show that it is a good agreement for applying this circularly polarized patch antenna to IoT applications with the Sub-1 GHz wireless technology.