Parameter Optimization of Staircase Shaped Co-Planar Waveguide Monopole Antenna with Modified Ground Plane for Radio-Frequency Energy Harvesting Application

Abstract

Co-planar waveguide (CPW) fed monopole antenna is a compact wideband antenna that is easy to fabricate and integrate with any RF circuitry. However, this antenna often suffers low gain and modifications are needed to create a deep resonance. In this work, a compact CPW fed monopole antenna is designed and optimized to resonate at 5.85 GHz Wi-Fi frequency band for RF energy harvesting application. The proposed antenna with a small size of 40 mm × 30 mm × 1 mm is composed of a staircase shaped radiating element fed by a CPW feed line, and an inverted stair-style ground. The antenna yields a high gain of 4.152 dB and wide bandwidth of 1.63 GHz or 27.86% impedance bandwidth. The optimization of the length of feedline and ground radiating elements through parametric sweeps show the most significant improvement of performance in terms of gain. The surface current is evenly distributed across the antenna with a higher concentration on the feeding area and edges of the main patch due to the stair-case shape and optimization of the feedline’s length. The performance of the antenna is evaluated for feasibility in energy harvesting application using Friis transmission approximation and it was found that the antenna has an average of 34.77% improvement in received power when compared to a reference antenna with the same size and operating frequency. The monopole antenna proposed in this work manages to have a high gain while maintaining miniature size without the need of any parasitic material.