Analyzing and Maximizing the Power Harvesting Efficiency of a Textile Rectenna Through Reflector-Based Shielding

Wearable rectennas harvest power from off-body sources; shielding mechanisms such as microstrip antennas' ground planes are typically used to reduce absorption by the body. This work investigates the use of unconnected reflectors to improve textile rectennas' harvesting capabilities. A high-efficiency rectenna using a textile-based rectifier, achieving over 40% RF-DC efficiency from -20 dBm power, and a monopole is investigated with different clothing layers in the presence and absence of a reflector. It is shown that a textile reflector can improve the DC output of a rectenna, on an external clothing layer, by over 100% through improving the measured gain by 2.4 dB. However, for rectennas with less than 2.0 mm clearance from the body, a reflector can have detrimental effect on the rectenna. The proposed reflector-backed rectenna achieves a wearable harvesting efficiency of 40%., from an ultra-low power density of 0.3 mu W/cm(2), demonstrating significant sensitivity improvement over state-of-the-art rectennas.