Backscatter radios used for gigabit-data rate mmWave communications

Researchers have developed a low-cost way for backscatter radios to support high-throughput communication and 5G-speed Gb/sec data transfer using a single transistor. 

Backscatter radios
Printed mmWave array prototype for Gbit-data rate backscatter communication (Credit: John Kimionis, Nokia Bell Labs)

The breakthrough by researchers at the Georgia Institute of Technology (GATECH), Nokia Bell Labs, and Heriot-Watt University could lead to low cost, low power 5G Internet of Things (IoT) networks.

Backscatter radios - passive sensors that reflect rather than radiate energy - are known for their economy, low-complexity, and battery-free operation, making them a potential key enabler of such networks but they typically feature low data rates, and their performance depends on the surrounding environment.

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To overcome this, the team employed a unique modulation approach in the 5G 24/28GHz bandwidth and demonstrated that these passive devices can transfer data safely and robustly from virtually any environment. The findings have been reported in Nature Electronics.

According to GATECH, mmWave communications is considered ‘the last mile’ for broadband, with directive point-to-point and point-to-multipoint wireless links. This spectrum band is said to offer advantages including wide available GHz bandwidth, which enables very large communication rates, and the ability to implement electrically large antenna arrays, enabling on-demand beamforming capabilities. However, such mmWave systems depend on high-cost components and systems.

"Typically, it was simplicity against cost. You could either do very simple things with one transistor or you need multiple transistors for more complex features, which made these systems very expensive," said Emmanouil (Manos) Tentzeris, Ken Byers Professor in Flexible Electronics in Georgia Tech's School of Electrical and Computer Engineering. "Now we've enhanced the complexity, making it very powerful but very low cost, so we're getting the best of both worlds."

"Our breakthrough is being able to communicate over 5G/millimetre-wave [mmWave] frequencies without actually having a full mmWave radio transmitter - only a single mmWave transistor is needed along much lower frequency electronics, such as the ones found in cell phones or Wi-Fi devices. Lower operating frequency keeps the electronics' power consumption and silicon cost low," added first author Ioannis (John) Kimionis, a Georgia Tech Ph.D. graduate now a member of technical staff at Nokia Bell Labs. "Our work is scalable for any type of digital modulation and can be applied to any fixed or mobile device."

The researchers are said to be the first to use a backscatter radio for gigabit-data rate mmWave communications, while minimising the front-end complexity to a single high-frequency transistor. GATECH added that their breakthrough included the modulation as well as adding more intelligence to the signal that is driving the device.

"We kept the same RF front-end for scaling up the data rate without adding more transistors to our modulator, which makes it a scalable communicator," Kimionis said in a statement.

The technology opens up a host of IoT 5G applications, including energy harvesting, which Georgia Tech researchers recently demonstrated using a specialised Rotman lens that collects 5G electromagnetic energy from all directions.

Tentzeris said additional applications for the backscatter technology could include ‘rugged’ high-speed personal area networks with zero-power wearable/implantable sensors for monitoring oxygen or glucose levels in the blood or cardiac/EEG functions; smart home sensors that monitor temperature, chemicals, gases, and humidity; and smart agricultural applications for detecting frost on crops, analysing soil nutrients, or tracking livestock.