Liverpool team tune into reconfigurable liquid antennas

Antennas, which are used in everything from mobile phones to radar, convert radio waves into electrical signals. The devices are typically built from metals such as copper, which have good conductivity.

However, metal antennas tend to be large, heavy and expensive, and cannot be reconfigured to operate across different frequencies. This is likely to become an increasing limitation as we move towards greater wireless communication between even tiny everyday devices in the “Internet of Things”.

Now, in an EPSRC-funded project, researchers at Liverpool University are hoping to develop small, transparent antennas that could be used in future 5G wireless networks, and in machine-to-machine communication.

Liquids, including water, are known to be capable of acting as an antenna, according to Professor Yi Huang, in the Department of Electrical Engineering and Electronics, who is leading the project.

“Liquids like water are transparent, which makes them attractive from an appearance perspective,” said Huang.

“The wavelength [of an electromagnetic signal] is also much shorter in liquid than in free space or metal,” he said.

Since signal wavelength is directly linked to the size of antenna, this could allow the devices to be built at much smaller sizes. “If the wavelength in free space is one metre, in water it would only be around 10 centimetres,” he said.

However, the drawback with using water alone as an antenna is that the liquid freezes when the temperature drops below 0 degrees Celsius, he said.

So the researchers hope to identify other, more suitable liquids that can be used as antennas as part of the project, which also involves BAE Systems and Chinese telecommunications company Huawei. They plan to investigate ionic liquids - or liquid salts - for example, and even anti-freeze, said Huang.

The liquids will be tested for low signal loss, thermal and mechanical stability, and their ability to operate in temperatures ranging from -30 to +60 degree C. The researchers will also investigate whether the liquids can transmit frequencies ranging from kHz to GHz, and have Radio Frequency and microwave power range of up to 100kW.