Digitally Tuneable Mobile Antenna Could Unlock 5G Wireless

The team’s method could mean less space is needed for phone antennas, meaning less constricted phone design. (Image courtesy of Aalto University.)

The next generation of wireless is coming sooner or later, and many expect it will be sooner. 5G is currently predicted to arrive by about 2020 to address growing demands for data and performance. The one hiccup in this forecast is that we don’t yet have the technology or standards in place to get there, but rest assured that research is well underway.

A team of engineers from Aalto University in Finland is doing their part by studying a new method of antenna design that may prove necessary to realize 5G level performance.

Frequency Reconfigurable Antennas

Current mobile antennas are under a lot of stress. For one, they’re subject to stricter and stricter performance requirements as communications technology evolves. Second, they’re expected to cover a lot of ground, as different countries have different frequency bands available for use. Lastly, they’re limited by the small space available in modern smartphones, and a decrease in size degrades their performance.

The Aalto engineers have proposed a novel method of frequency reconfigurable antennas that may circumvent these concerns. Frequency reconfigurable antennas with tuneable capacitor matching networks already exist, but the team’s antenna architecture does away with the need for space-hogging analog components.

The method involves using several antenna elements along with several transceivers, instead of one of each. By placing the antennas in close proximity to each other, it’s possible to take advantage of mutual coupling between them. Using digital techniques, the researchers were able to adjust the amplitudes of the transmit signal to each antenna in such a way so as to create destructive interference for the reflected waves.

“Traditionally one antenna works with either one or a few different frequencies,” said researcher Jari-Matti Hannula. “Now we can take advantage of advanced digital electronics and combine several small antenna elements to work together as one antenna that can be made to operate digitally with any frequency.”

The team’s antenna concept involves multiple antenna/transceiver elements. By properly weighting the incident signals ai, you can minimize the reflected power and optimize matching efficiency. (Image courtesy of IEEE Antennas and Wireless Propagation Letters.)

The technique allows for frequency tunability with what will hopefully be a much lower PCB footprint than current methods. While the technique requires multiple transceivers, the rate of integrated circuit advancement as compared to the rate of passive analog component advancement will likely see the new concept become feasible quite soon.

The engineers have demonstrated the new technique with simulations, but have yet to realize a physical prototype. There’s also a host of remaining issues to address, such as the best antenna structures to use and how to design for resonance frequencies and coupling. Regardless, the work is promising and may be the path forward to realizing 5G.

“In this way, many smartphone applications like GPS, Bluetooth and Wi-Fi will no longer need their own antennas,” explained Hannula. “Instead, all of the phone's data transfer can take place through one digitally controlled antenna. This in turn makes phone design easier and enables a larger screen size relative to phone size as the antenna does not require so much space.”

You can read the team’s research paper in IEEE Antennas and Wireless Propagation Letters. For more from the world of smartphones, check out Portable Smartphone Laboratory Detects Cancer.