Scientists from the Centre for Wireless Technology at Malaysia’s Multimedia University jointly with their colleagues from Canada’s Institut national de la recherche scientifique and Al Ain University in the UAE have developed a compact broadband antenna for harvesting scattered radio frequency energy. The device can receive radio waves across a wide range of frequencies, from cellular and digital television signals to Wi-Fi, and convert them into electricity.
Today’s environment is virtually saturated with electromagnetic waves. LTE and GSM base stations, Wi-Fi access points and television broadcast transmitters emit radio signals on a continuous basis. While this energy is typically used for data transmission only, it can be physically converted into a power source for low-power electronics. The biggest technical challenge is that these signals are distributed across various frequency ranges, whereas most standard antennas operate in a narrow band. To achieve effective energy harvesting from multiple frequency areas at the same time, one needs a broadband antenna that will be compact enough to be integrated into sensors and sensor nodes.
The researcher team has proposed an original solution focusing on design geometry. Its key element is a rectangular slot in a substrate made of FR-4 material, a fiberglass laminate based on glass fiber and epoxy resin, which is used in electronics to produce printed circuit boards. The slot accommodates three elements: an inverted T-shaped protrusion and two E-shaped protrusions on the sides. This configuration creates a few resonant modes at different frequencies. In simple terms, the antenna combines the properties of several resonators in a single compact package. By selecting the dimensions and relative positions of these elements during computer modeling, the researchers managed to bring individual resonant peaks together into a single broad operating band.
The resulting device, which measures about 100 x 76 mm, is capable of stable operation in the range from 0.84 GHz to 1.89 GHz. Its maximum gain reaches 4.86 dBi. This means that the antenna concentrates the signal in the primary receiving direction about three times more efficiently than a conventional omnidirectional antenna. This feature makes it possible to reliably receive signals from digital television stations, GSM 900, GSM 1800 and other systems operating in this frequency range.
Tests conducted in an anechoic chamber confirmed the agreement between calculations and experimental parameters. After connecting a rectifier, which converts the variable radio frequency signal to DC voltage, the conversion efficiency rate rose close to 80%.
Going forward, solutions of this kind could improve the autonomy of smart home sensors, industrial equipment and environmental monitoring systems, reducing dependence on conventional batteries and streamlining the operation of distributed sensor networks.
