Transparent Compact Rectenna (TCR) Based Continuous Wireless Charging System (CWCS) for Smart Watches by Utilizing Available 5G Microwave Radiations

This paper represents a compact, transparent microwave energy harvesting (MEH) system at a 3.3 GHz frequency band to assist the rechargeable battery system of the smart watch. The operating frequency of the proposed system is targeted to the 5G and beyond communication’s frequency bands. It is feasible to integrate a CPW-fed transparent folded monopole circular patch antenna onto the dial of the smart watch. Transparent conductive materials ITO and PET as substrates are utilized to design the proposed antenna to enhance the transparent efficiency of the rectenna system. The radiated gain of the proposed antenna is achieved of 2.16 dB at 3.3 GHz, with an omnidirectional radiating field pattern. Further, a microwave energy harvesting system is designed that consists of an antenna, a matching circuit, and a voltage doubler rectifier circuit by utilizing the Schottky diode (HSMS2860). The maximum output voltage of the rectenna system is obtained at 0.926 volts, while the maximum output power of 0.5484 (mW) is achieved at 3.3 GHz. The maximum RF-dc conversion efficiency (PCE%) of the proposed microwave energy harvesting system is obtained at 55%.