System Bits: Feb. 6

Low-latency data compression; neuromorphic computing material; touchscreen pressure sensors.


Compressing data in vehicles
As the number of cameras in automobiles is on the rise with the move to autonomous vehicles, internal vehicle networks are being pushed to their limits from the flood of data. While special compression methods reduce the amount of video data, they also exhibit a high degree of latency for coding. But now, Fraunhofer researchers have adapted video compression in such a way they say a latency is almost no longer perceivable.

Cameras are installed, for example, in reverse lamps. They help with parking or detect obstacles. To minimize the size of the image data, video compression techniques are used. Thanks to the development work of the Fraunhofer HHI, this now happens almost without delay.
Source: Fraunhofer

In new vehicle models, there can be up to 12 cameras in new vehicle models, mostly in the headlights, taillights, and side mirrors while an on-board computer built into the car uses the data for the lane assistant, parking assist system or to recognize other road users or possible obstacles, for example.

And when autonomous vehicles really begin hitting the road, there will be even more strain on the internal data networks of vehicles, which can currently process a data volume of around one gigabit per second. In HD quality, this data quantity is already reached with one camera, but compression methods help here.

Fraunhofer researchers have developed two video coding standards H.264/Advanced Video Coding (AVC) and H.265/MPEG High Efficiency Video Coding (HEVC) so that the data quantities can be sharply reduced. In this way, more than ten times the quantity of data can be transmitted.

Normally, 30 to 60 images per second are sent from a camera to the vehicle’s central computer, and by compressing the image data, a small delay in transmission occurs, known as the latency. The reason for this is that the methods compare an image with those that have already been transmitted in order to determine the difference between the current image and its predecessors. The networks then only send the changes from image to image. This determination takes a certain amount of time.

This loss of time can be of decisive importance in road traffic, so in order to avoid latency, the team only use special mechanisms of the H.264-coding method, whereby determining the differences in individual images no longer takes place between images, but within an image. This makes it a low-latency method. With this method, the delay is now less than one image per second, almost real time, therefore the H.264 method can now be used for cameras in vehicles.

The technology is implemented in the form of a special chip. In the camera it compresses the image data, and in the on-board computer it decodes them.

The researchers in Berlin have had their method patented and sell their know-how to the industry in the form of a license.

In the next stage, the researchers also want to transfer their method to the HVEC standard and put their experience to good use in upcoming standardization formats.

Aerospace, neuromorphic computing materials
First came the switch. Then the transistor. Now another innovation stands to revolutionize the way we control the flow of electrons through a circuit: vanadium dioxide (VO2). According to EPFL researchers, a key characteristic of this compound is that it behaves as an insulator at room temperature but as a conductor at temperatures above 68°C. This behavior – also known as metal-insulator transition – is being studied in an ambitious EU Horizon 2020 project called Phase-Change Switch. EPFL was chosen to coordinate the project.

Due to the array of high-potential applications that could come out of this new technology, the project has attracted two major companies – Thales of France and the Swiss branch of IBM Research – as well as other universities, including Max-Planck-Gesellschaft in Germany and Cambridge University in the UK. Gesellschaft für Angewandte Mikro- und Optoelektronik (AMO GmbH), a spin-off of Aachen University in Germany, is also taking part in the research.

Vanadium dioxide’s unique properties make it perfect for outperforming silicon and giving rise to a new generation of low-power electronic devices. Under the Phase Change Switch project (, which is being funded by the EU’s Horizon 2020 research program and coordinated by EPFL researchers, engineers have shown how this compound can be used to create programmable radiofrequency electronic functions for aerospace communication systems. Other applications – such as in neuromorphic computing and artificial intelligence – are also on the cards. Source: EPFL

Scientists have long known about the electronic properties of VO2 but haven’t been able to explain them until know. It turns out that its atomic structure changes as the temperature rises, transitioning from a crystalline structure at room temperature to a metallic one at temperatures above 68°C, the researchers explained. This transition happens in less than a nanosecond – a real advantage for electronics applications. “VO2 is also sensitive to other factors that could cause it to change phases, such as by injecting electrical power, optically, or by applying a THz radiation pulse,” says Adrian Ionescu, the EPFL professor who heads the school’s Nanoelectronic Devices Laboratory (Nanolab) and also serves as the Phase-Change Switch project coordinator.

However, unlocking the full potential of VO2 has always been tricky because its transition temperature of 68°C is too low for modern electronic devices, where circuits must be able to run flawlessly at 100°C.

Two EPFL researchers – Ionescu from the School of Engineering (STI) and Andreas Schüler from the School of Architecture, Civil and Environmental Engineering (ENAC) – may have found a solution to this problem, according to their joint research published in Applied Physics Letters in July 2017. They found that adding germanium to VO2 film can lift the material’s phase change temperature to over 100°C.

Even more interesting findings from the Nanolab – especially for radio frequency applications – were published in IEEE Access on 2 February 2018. For the first time ever, scientists were able to make ultra-compact, modulable frequency filters. Their technology also uses VO2 and phase-change switches, and is particularly effective in the frequency range crucial for space communication systems (the Ka band, with programmable frequency modulation between 28.2 and 35 GHz).

These promising discoveries are likely to spur further research into applications for VO2 in ultra-low-power electronic devices. In addition to space communications, other fields could include neuromorphic computing and high-frequency radars for self-driving cars.

Touchscreen pressure sensor arrays
Touchscreens on mobile handheld devices can detect if and where a user is touching the screen, but standard technology cannot determine how much pressure is being exerted, until now.
Researchers at the University of California San Diego and the University of Texas at Austin have demonstrated a new technology for ‘force sensing’ that can be added to any type of display, including flexible devices, and potential other uses go far beyond touch screen displays on mobile devices.

The Integrated Electronics and Biointerfaces Lab’s zinc oxide touchscreen array fixated on a carrier wafer and tested with a commercial (Synaptics, Inc.) display driver. Source: UCSD

Before he graduated from UC San Diego’s Jacobs School of Engineering, electrical and computer engineering alumnus Siarhei Vishniakou (Ph.D. ’16) worked with colleagues including his advisor, electrical engineering professor Shadi Dayeh, to spin off a startup company, Dimensional Touch. He was also accepted into the NSF I-Corps I and II programs that help academics commercialize new technology.

L-R: Professor Shadi Dayeh and Siarhei Vishniakou
Source: UCSD

Since then, the team has demonstrated that zinc oxide-based thin-film transistor sensors can be easily integrated with existing commercial integrated circuits widely used to control touch screens (in which a variant of zinc oxide, indium gallium zinc oxide, is already used).

“It has been known for generations that zinc oxide has good piezoelectric properties and manufacturers already use indium gallium zinc oxide in displays,” said Dayeh. “So it seemed that using zinc oxide in a thin-film transistor would seamlessly integrate into the process flow already used by manufacturers of touch screens.”

The team developed and optimized the technology so that it simultaneously functions as a transistor and as a force sensor.

They determined that they could improve the transistor performance and the pressure-sensitivity by doing the zinc oxide deposition in an oxygen-rich environment. The cost of the technology is also reduced because it can be integrated into a display at the backplane level.

The researchers believe the technology is still ripe for commercialization, but may require fabrication of a near-final device that would represent a real product that a manufacturer could customize and sell without too much further R&D.

There are other companies trying to bring force sensing into touchscreens, but this one has no moving parts, is scalable to large dimensions, and is capable of integration into the display backplane using existing manufacturing equipment, the team said. Apple’s 3D Touch is one potential rival, but it adds dramatically more weight to a smartphone compared to what the zinc oxide technology would weigh when it’s integrated directly to the backbone of the display, they said.

In addition to displays, the researchers believe that zinc oxide can add a new dimension to videogames given that gaming involves a lot of interaction with the game and other players, and because the player feels the pressure and can see a near-real-time response to that pressure, this technology could provide another tool in the gamer’s toolbox.

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