Slots and stubs incorporated annular ring-shaped compact microstrip antenna with circular polarization characteristics for wireless UWB communication systems

Abstract

A circularly polarized (CP) antenna with ultra-wideband resonance and a broad axial ratio bandwidth is designed for UWB communication systems. The prescribed design comprises of a modified annular ring-shaped radiator and a modified step-graded slots loaded partial ground plane. The projected antenna is prototyped on FR4 substrate of 35×30×1.6 mm3. To achieve wide axial ratio bandwidth, a rectangular vertical slot is inserted into the radiating patch and two stubs are embedded into the monopole ground plane, which is configured with step graded rectangular slots. The simulation results are verified by testing the fabricated protype. The proposed design operates at UWB spectrum with an ultra-wide impedance bandwidth (IBW) of 134.57%, centered at 10.7 GHz, covering 3.5 GHz to 17.9 GHz frequency spectrum. Furthermore, it demonstrates circular polarization characteristics with a broad axial ratio bandwidth (ARBW) of 96.29% expanding from 3.5-10 GHz (6500 MHz). Its peak gain reaches to 8.7 dBi and a maximum radiation efficiency of 95% is achieved within the operating band. The results (measured and simulated) obtained in terms of S11, axial ratio, gain and efficiency and radiation patterns exhibit high agreement. The presented antenna could be a suitable choice for 5.5 GHz Worldwide Interoperability for Microwave Access (Wi-Max), 5.2/5.8 GHz Wireless local area network (WLAN), X-band satellite communication (downlink: 7.25-7.745 GHz, uplink: 7.9-8.4 GHz), UWB communication systems, and other applications in microwave C, X, Ku bands due to its superior characteristics.