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