Edinburgh Napier University

  Energy-constrained Internet of Things (IoT) and wireless sensor networks (WSNs) require sustainable power solutions to minimise battery maintenance and ensure continuous operation. Simultaneous wireless information and power transfer (SWIPT) enables RF energy harvesting while maintaining communication capabilities, reducing reliance on batteries. This paper presents a compact dual-band 4-port circularly polarised (CP) antenna for SWIPT at 3.5 GHz and 5.8 GHz, eliminating the need for an impedance-matching network to reduce insertion loss and circuit complexity while enhancing RF harvesting efficiency. The multiport antenna has high port isolation (-30 dB) and suppressed spurious radiation. Two ports support wireless communication, while the remaining two integrate rectifiers, achieving a power conversion efficiency (PCE) exceeding 60% at -10 dBm input power.

The antenna features a compact four-port circular patch with a slot for miniaturization, while a defective ground structure (DGS) enhances bandwidth and isolation. Figure 1a illustrates the antenna's configuration, detailing the circular patch, slot, and port configuration. Figure 1d presents the integration of the rectifiers with the antenna system, demonstrating the RF-to-DC conversion process. The simulations results include S-parameter measurements, as shown in Figures (1b), with S33 spanning 3.4–6.8 GHz, S11 covering 3.2- 3.7 GHz. Isolation plots (S13, S12, S34, S23, S14) in Figures (1c) confirm excellent port decoupling, ensuring minimal cross-talk. These results demonstrate the antenna’s suitability for compact, low-power SWIPT applications in IoT and WSNs, offering an efficient and integrated solution for RF energy harvesting and wireless communication.