Design, Simulation, and Practical Realization of a Compact 2.4 GHz Printed Circular Monopole Antenna for RF Energy Harvesting

Abstract

Radio-frequency energy harvesting requires a receiving antenna that combines compact dimensions with effective impedance matching at the target frequency. This study presents the design, simulation, fabrication, and experimental evaluation of a single-band printed circular monopole antenna intended for operation at 2.4 GHz within the Wi-Fi/ISM band. The antenna employs a circular radiating element, a microstrip feed line, and a partial ground plane on a CEM-1 (FR4) substrate, with overall dimensions of 70 × 50 mm². The design was modelled and evaluated using CST Microwave Studio, and its performance was assessed in terms of voltage standing wave ratio, reflection coefficient, bandwidth, surface-current distribution, radiation pattern, and gain. The simulated antenna exhibited a VSWR of 1.0027 and an S11 reflection coefficient of −31.608 dB at 2.4 GHz. The reported impedance bandwidth was approximately 188 MHz. Surface-current analysis showed strong current concentration near the feed region followed by a broadly symmetrical distribution over the circular radiator. The simulated radiation characteristics were stable in the principal planes, with a quasi-omnidirectional three-dimensional pattern. A fabricated prototype was subsequently assessed using a LiteVNA vector network analyser. The measured reflection coefficient was approximately −28 dB at the target frequency, indicating close correspondence with the simulated resonance. Overall, the results demonstrate the practical realisation of the proposed compact receiving antenna for 2.4 GHz RF energy-harvesting applications.