Wearable coupled-quarter-mode SIW antenna platform with hybrid kinetic and ambient-light energy harvesting

As key enablers for smart fabric interactive textile (SFIT) systems, textile antenna systems and platforms need to be energy-efficient, low-profile and should guarantee a stable wireless body-centric communication link. Using multiple energy harvesters on and in the antenna platform is highly recommended to enable autonomous SFIT systems. Different sensors could be added to the system for monitoring the environmental and/or biophysical parameters of rescue workers, military personnel, and other safety workers. Therefore, a wearable coupled-quarter-mode (coupled-QM) substrate-integrated waveguide (SIW) antenna with optimally, seamlessly integrated hybrid kinetic and ambient-light energy harvesters is proposed. Two QM cavities are coupled via a non-resonant slot to create a compact antenna covering the [2.4; 2.4835] GHz Industrial, Scientific and Medical (ISM) band. The antenna platform fully consists of textile materials, being protective rubber foam and copper taffeta, enabling its unobtrusive integration into protective clothing. A novel, compact way of deploying a kinetic energy harvester inside the substrate, combined with flexible power management electronics on the antenna feed plane and a flexible ambient-light photovoltaic cell on the antenna plane, is proposed. The integrated antenna platform exhibits a measured impedance bandwidth of 307 MHz, a radiation efficiency of 88.57% and maximum gain of 3.74 dBi at 2.45 GHz. Wearing the antenna platform around a person's wrist resulted in an average harvested power of 229.8 µW when walking in an illuminated room.