A Miniaturized Coupler-Integrated Rectenna Element to Eliminate Hybrid-Coupler Circuit for Polarization Insensitive Wireless Power Transmission

In wireless power transfer (WPT), rectenna is utilized to wirelessly charge the Internet of Things (IoT) nodes. The harvesting performance of the rectenna depends on the wave polarization; thus, a polarization-insensitive (PoI) rectenna is desired to allow free rotation of the IoT nodes. Typically, a dual linearly polarized (DLP) antenna is employed for this, and to achieve full PoI, the prior arts emphasize the necessity to insert a hybrid coupler (HC) between the rectifiers and the DLP antenna. However, the use of complex circuits, i.e., HC, matching networks (MNs), and rectifiers, degrades the power conversion efficiency (PCE) and increases rectenna size. Therefore, in this article, a new rectenna system is analytically evolved having an HC-like feature to achieve PoI without employing an HC circuit. Hence, a fully integrated dual circularly polarized rectenna (DCPR) is proposed which simultaneously achieves the desired PoI performance together with enhanced PCE and miniaturization. The proposed design was experimentally validated. The results show a 126% enhancement in PCE by the proposed DCPR over the conventional HC-based rectenna where both achieve PoI and the former is miniaturized. Hence, the proposed DCPR is a good rectenna contender for wireless charging of randomly oriented miniature IoT nodes.