Backscatter advance promises near-zero-power IoT 5G communications

Technology News | June 29, 2021

By Rich Pell

Wireless Communications Flexible Electronics RF transmission Medical Electronics IoT Energy Harvesting Sensing / Conditioning Power Management Wearables Analog

While backscatter radios – passive sensors that reflect rather than radiate energy – are known for their low-cost, low-complexity, and battery-free operation, they typically feature low data rates and their performance strongly depends on the surrounding environment. Previously, to achieve higher performance from this technology required expensive and multiple stacked transistors.

However, say the researchers, by employing a unique modulation approach in the 5G 24/28-gigahertz (GHz) bandwidth, they have shown that a millimeter-wave (mmWave) modulator and antenna array for backscatter communications can transfer data safely and robustly from virtually any environment. Traditionally, mmWave communications is used for directive point-to-point and point-to-multipoint wireless links in broadband communications.

This spectrum band offers many advantages, including wide available gigahertz bandwidth, which enables very large communication rates, and the ability to implement electrically large antenna arrays, enabling on-demand beamforming capabilities. However, say the researchers, such mmWave systems depend on high-cost components and systems.

“Typically, it was simplicity against cost,” says Emmanouil (Manos) Tentzeris, Ken Byers Professor in Flexible Electronics in Georgia Tech’s School of Electrical and Computer Engineering (ECE). “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. Now we’ve enhanced the complexity, making it very powerful but very low cost, so we’re getting the best of both worlds.”

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

“Our breakthrough,” says Ioannis (John) Kimionis, a Georgia Tech Ph.D. graduate now a member of technical staff at Nokia Bell Labs, “is being able to communicate over 5G/millimeter-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. Our work is scalable for any type of digital modulation and can be applied to any fixed or mobile device.”

The researchers kept the same RF front-end for scaling up the data rate without adding more transistors to their modulator, which makes it a scalable communicator and demonstrates how a single mmWave transistor can support a wide range of modulation formats. The technology, say the researchers, opens up a host of IoT 5G applications, including energy harvesting, which Georgia Tech researchers recently demonstrated using a specialized Rotman lens that collects 5G electromagnetic energy from all directions.

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, analyzing soil nutrients, or even livestock tracking.

The researchers say the backscatter technology breakthrough also reflect a goal to “democratize communications.”

“Throughout my career,” says Tentzeris, “I’ve looked for ways to make all types of communication more cost efficient and more energy efficient. Now, because the whole front end of our solution was created at such low complexity, it is compatible with printed electronics. We can literally print a mmWave antenna array that can support a low-power, low-complexity, and low-cost transmitter.”

Affordable printing, says Tentzeris, is crucial to making their backscattering technology market viable. For more, see “A printed millimeter-wave modulator and antenna array for backscatter communications at gigabit data rates.”