High-Efficiency Sub-1 GHz Flexible Compact Rectenna based on Parametric Antenna-Rectifier Co-Design

This work presents a high-efficiency, high-sensitivity, compact flexible rectenna based on a high-impedance folded dipole antenna, for sub-1 GHz license-free applications. A voltage-doubler rectifier is studied parametrically, using Electromagnetic- Harmonic Balance co-simulation, to extract the optimal load and source impedances for maximum power conversion efficiency (PCE), using an iterative source and load tuning approach. The proposed antenna is then studied parametrically and designed to directly conjugate the rectifier's impedance eliminating the matching network and its associated losses. The integrated rectenna is ultra-compact (area=0.0122λ²0) and is fabricated on a 25 µm-thick flexible low-cost polyimide substrate. The proposed rectenna achieves a remarkable PCE of 43% and 83% at -20 and -4 dBm, respectively. Furthermore, a 1-V DC output is achieved across a 20kΩ load (optimal impedance) from -9 dBm input. The rectenna demonstrates a -3 dB (50% relative PCE) fractional-bandwidth of 7.9% (813–880 MHz), covering the 868 MHz license-free band.