Hemispherical Rectenna Arrays for Multi-Directional, Multi-Polarization, and Multi-Band Ambient RF Energy Harvesting

UCLA researchers in the Department of Electrical Engineering have developed a system that can receive RF waves in different frequency bands, from different directions, and with different polarizations to maximize energy harvested from ambient radio-frequency signals.

Harvesting radio-frequency (RF) energy from the surrounding ambient is potentially a sustainable and environmentally responsible source of energy. Majority of ambient RF energy is distributed across frequency bands for cellular data communications and WiFi communications. These ambient RF waves are also both multi-polarized and multi-directional. Thus, to maximize harvested energy output requires a system that can receive RF waves in different frequency bands, from different directions, and with different polarizations.

UCLA researchers proposed and simulated a new system design using an array of rectennas (an antenna and a rectifier circuit) to achieve high power energy harvesting in different frequency bands, from different directions, and with different polarizations. This technology demonstrated experimentally an antenna element that operates at high-density ambient RF energy bands of 900MHz (GSM900), 1.8GHz (GSM1800), and 2.4GHz (WiFi). The designed system is estimated to be capable of delivering 7 - 12.5 uW DC power output in total.

The UCLA researchers have partially demonstrated experimentally the proof-of-concept product: a functional single antenna, and a single rectifier circuit operating in one frequency band (0.9GHz). A system level design has also been proposed that can be implemented in real world and system parameters have been estimated.