Wearable Flexible Antenna For Microwave Wireless Power Transfer

This paper reports a wearable flexible antenna for microwave wireless power transfer applications. The resonant frequencies of the proposed wearable antenna are designed at 2.40 GHz and 5.20 GHz, which can be obtained from a commercialized WiFi band. It has a reflector imprinted on the reverse to prevent the loading effect that the lossy human tissue may cause. The proposed wearable antenna can be made very compact with a 50 Ω RF-to-DC micro-chip converter and an internal matching loop for replacing the external complex matching circuits. Experimental data show the optimal load of the proposed wearable antenna is 20 kΩ at 2.44 GHz and 56 kΩ at 5.23 GHz. The maximum wireless output powers are measured as ~ 7.2 mW at 2.44 GHz and ~ 0.25 μ W at 5.18 GHz, respectively, which are sufficient for ultralow-powered wearable applications. A proof-of-concept of the microwave far-field wireless power transfer was demonstrated by successfully lighting an LED.