Power/Performance Bits: Sept. 8

Backscatter radios for 5G
Researchers at the Georgia Institute of Technology, Nokia Bell Labs, and Heriot-Watt University propose using backscatter radios to support high-throughput communication and 5G-speed Gb/sec data transfer using only a single transistor.

“Our breakthrough 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 WiFi devices. Lower operating frequency keeps the electronics’ power consumption and silicon cost low,” said 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.”

Printed mmWave array prototype for Gbit-data rate backscatter communication. (Credit: John Kimionis, Nokia Bell Labs / Georgia Institute of Technology)

“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, professor in flexible electronics at Georgia Tech. “Now we’ve enhanced the complexity, making it very powerful but very low cost, so we’re getting the best of both worlds.”

A single mmWave transistor can support a wide range of modulation formats, Kimionis noted. “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.”

Key to making the device viable commercially is affordable printing technology, the team said. “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,” said Kimionis.

Small quantum random number generator
Researchers from the University of Science and Technology of China and Zhejiang University developed a quantum random number generator (QRNG) that small and low power enough to be portable. It utilizes a photonic IC with optimized real-time postprocessing for extracting randomness from quantum entropy source of vacuum states.

“Recently, the technology of integrated quantum photonics has exhibited significant advantages in terms of size reduction,” said Jun Zhang of the University of Science and Technology of China. “In this work, we further prove that such technology could be used for ultrafast, real-time quantum random number generation.”

The group’s chip uses indium-germanium-arsenide photodiodes and a transimpedance amplifier integrated onto a silicon photonics chip that includes several couplers and attenuators. Combining these components allows the QRNG to detect signals from a quantum entropy source with significantly improved frequency response.

“The surprising point in our work is that the high-frequency response performance of the final photonic integrated chip is better than expected,” Zhang said.

Once randomness signals are detected, they are processed by a field programmable gate array, which extracts truly random numbers from the raw data. The resulting device can generate numbers at 18.8 gigabits per second, which the team said is a new world record. The random numbers can then be sent to any computer via a fiber optic cable. Plus, the chip measures 15.6 by 18.0 millimeters, smaller than most current QNRG modules or instruments.

“Based on our present work, in the future, we will develop a low-cost single chip of QRNG with moderate random bit rate, at the level of megabits per second, for commercial uses,” Zhang said. “Such a single chip could be very useful in diverse electronic systems requiring random numbers or signals and even in mobile phones to improve the security.”

Dissolving pacemaker
Researchers at Northwestern University and George Washington University developed a pacemaker that can safely dissolve in the body when it’s no longer needed. The wireless, battery-free device could be used for patients that need temporary pacing, such as after cardiac surgery or while waiting for a permanent device. It is absorbed by the body over the course of five to seven weeks.

It wirelessly harvests energy from an external, remote antenna using near-field communication protocols, removing the need for external batteries or leads.

“Sometimes patients only need pacemakers temporarily, perhaps after an open heart surgery, heart attack or drug overdose,” said Dr. Rishi Arora, a cardiologist at Northwestern Medicine. “After the patient’s heart is stabilized, we can remove the pacemaker. The current standard of care involves inserting a wire, which stays in place for three to seven days. These have potential to become infected or dislodged.”

“The transient electronics platform opens an entirely new chapter in medicine and biomedical research,” said Igor Efimov, a professor of biomedical engineering at George Washington University. “The bioresorbable materials at the foundation of this technology make it possible to create whole host of diagnostic and therapeutic transient devices for monitoring progression of diseases and therapies, delivering electrical, pharmacological, cell therapies, gene reprogramming and more.”

The fully implantable device 250 microns thick and weighs less than half a gram. Soft and flexible, it encapsulates electrodes that softly laminate onto the heart’s surface to deliver an electrical pulse.

“Instead of using wires that can get infected and dislodged, we can implant this leadless biocompatible pacemaker,” Arora said. “The circuitry is implanted directly on the surface of the heart, and we can activate it remotely. Over a period of weeks, this new type of pacemaker ‘dissolves’ or degrades on its own, thereby avoiding the need for physical removal of the pacemaker electrodes. This is potentially a major victory for post-operative patients.”

By varying the composition and thickness of the materials in the device, it is possible to control the number of days it remains functional before dissolving.

“With further modifications, it eventually may be possible to implant such bioresorbable pacemakers through a vein in the leg or arm,” Arora predicts.