Millimeter-Wave Textile Antenna for on-Body RF Energy Harvesting in Future 5G Networks

Millimeter-Wave (mmWave) bands will be a key part of future 5G networks, with the 26 and 28 GHz bands being introduced first. The wide bandwidth aims to solve traffic-related issues. The projected high base-station density, highly directive transmitters, and the wide bandwidth make it a very promising RF energy harvesting (RFEH) source. Broadband antennas are necessary to harvest power efficiently from the full spectrum. This work presents the first antenna on textile for wearable ambient RFEH in the 26 GHz and 28 GHz bands. The antenna has an impedance bandwidth from 20 to 30 GHz, and exhibits a peak on-body gain of 7 dB with an omnidirectional radiation pattern for capturing ambient RF energy. The radiation efficiency on- and off-body was observed to be at least 40% and 60% respectively, between 24 and 30 GHz. A two-line microstrip dielectric characterization of the textile substrate in the mmWave band has been performed. The antenna has been fabricated on a 310 μm woven polyester substrate using etched ultra-thin Polyimide copper laminates with a minimum feature size of 150μm. A high robustness against human proximity has been demonstrated with a stable bandwidth and improved gain.