Research Bits: Feb. 21

High-quality ‘chirps’ for automotive, industrial mmWave radar

Imec demonstrated a low-power phase-locked loop (PLL) that generates high-quality frequency-modulated continuous-wave (FMCW) signals for mmWave radar, which can be used in short-range automotive and industrial radar applications. The FMCW radars popular in healthcare, automotive, and industrial send out sinusoidal waves that get larger with distance. These waves, called ‘chirps’, are used to tell distance as the chirp bounces back off an object and mingles with the outgoing chirps, explains imec in a press release. The FMCW signals have to be high-quality signals, however.

Imec’s innovation is a digitally calibrated charge-pump (CP) PLL that produces chirps as fast as 12µs, with as low as 41kHzrms error in frequency modulation (rms-FM-error). The low power comes in when PLL can power down after sending out chirps in one burst. Imec says the PLL has fast startup and resets, with the highly linear, high-quality chirp signals centered around 16GHz with a chirp bandwidth of 1.5GHz.

“Applications include in-cabin radar sensors to monitor presence, movements, and well-being of driver and passengers, as well as out-of-cabin sensors for parking assistance or vehicle detection,” said Ilja Ocket, program manager at imec. “Our PLL also opens doors to robotics radar applications – think of on-cobot radar sensors to enhance safety and efficiency of human-robot interaction in industrial environments – as well as to radar sensors mounted on small moving objects or vehicles such as drones. At ISSCC, we are presenting a functional demo that integrates our CP-PLL with imec’s existing 140GHz radar receiver and transmitter blocks to showcase the potential of the technology for future automotive and industrial applications. The PLL can also be used for up-conversion to mmWave radar signals with other carrier frequencies, e.g., 80GHz.”

Jumping the Terahertz gap

Researchers from the Power and Wide-band-gap Electronics Research Lab (POWERlab) in EPFL’s School of Engineering have figured out a way to make electronic devices move data faster —operating at electromagnetic frequencies in the terahertz range (between 0.3-30 THz). Elison Matioli and Mohammad Samizadeh Nikoo etched patterned contacts at sub-wavelength distances onto a semiconductor made of gallium nitride and indium gallium nitride. Known as metastructures, these contacts make it possible to control electrical fields inside the device. This control can yield extraordinary properties that do not occur in nature, according to a press release.

“We found that manipulating radiofrequency fields at microscopic scales can significantly boost the performance of electronic devices, without relying on aggressive downscaling,” said Samizadeh Nikoo. The team used optics methods to avoid the terahertz gap in modern electronics.

“The ability to control induced radiofrequencies comes from the combination of the sub-wavelength patterned contacts, plus the control of the electronic channel with applied voltage. This means that we can change the collective effect inside the metadevice by inducing electrons (or not),” says Matioli.

Matioli seems to suggest giving up on transistor shrinking. “New papers come out describing smaller and smaller devices, but in the case of materials made from gallium nitride, the best devices in terms of frequency were already published a few years back,” said Matioli. “After that, there is really nothing better, because as device size is reduced, we face fundamental limitations. This is true regardless of the material used.”

The team published their findings in a recent paper in the journal Nature. Samizadeh Nikoo, M., Matioli, E. Electronic metadevices for terahertz applications. Nature 614, 451–455 (2023). https://doi.org/10.1038/s41586-022-05595-z

Quantum sensors sniff out correlations

A team from U.S. Department of Defense’s Argonne National Laboratory found a new method for sensing magnetic field strengths at multiple points simultaneously, according to a press release. Using quantum sensors, which can pick up the tiny magnetic fields arising from the motion of single electrons, the team found a way via spin-to-charge conversion to get accurate data, on which they ran a covariance. Through the conversion and covariance, the team gained access to atomic and subatomic details they didn’t have before, which is how they were about to find or disprove corrections in the quantum sensing data.

The team calls it covariance magnetometry, and it saves time after the initial time-hit on when taking the accurate measurements. The Q-NEXT quantum research center supported the team’s research.