A Novel Design of Broadband Circularly Polarized Rectenna With Enhanced Gain for Energy Harvesting

Device-to-device communication in the Internet of Things (IoT) enables seamless data exchange, aiding automation, monitoring, and control. Yet, sustainability challenges arise due to energy-limited devices. This paper presents a novel method for Indoor IoT sensors to function without batteries. A broadband rectenna on low-cost FR4 substrate is proposed, mitigating battery constraints. It integrates a circularly polarized (CP) antenna with an Artificial Magnetic Conductor (AMC) and a RF-to-DC rectifier. A coplanar waveguide fed CP (CPW-CP) antenna achieves a broad axial ratio bandwidth (ARBW) of 19.6% (AR <3 dB) spanning from 2.3 GHz to 2.8 GHz, boosting gain from 0.5-0.8 dBic to 5-6.5 dBic within the ARBW, courtesy of the AMC integration. A stable RF-DC rectifier, using a modified wideband resistance compression network (WRCN), attains a power conversion efficiency (PCE) exceeding 30% for input powers ranging from -10 dBm to 12 dBm, peaking at 65% for 7 dBm input power for a 2 kΩ load. PCE variation within ARBW is only 5-8%. The RF-DC rectifier is integrated with the enhanced gain CPW-CP antenna to form a rectenna which is fabricated and measured. The experimental results comply with the simulated results, and the experimental validation demonstrates the rectenna's effectiveness in charging a 0.1 pF capacitor within 2 ms in an indoor environment equipped with a Wi-Fi router. This innovative design marks a promising step towards addressing energy constraints in IoT devices, facilitating their long-term operation and deployment in diverse settings.