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New technology uses radio signals to display hidden and accelerating objects

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How m-Widar Works


Illustration of a laboratory setup for m-Widar: transmitters and receiver on the left, and a person behind a wall panel on the right. The inset in the lower right corner shows the corresponding image generated by the instrument. Credit: NIST

Researchers from the National Institute of Standards and Technology (NIST) and Wavsens LLC have developed a method of using radio signals to create real-time images and videos of hidden and moving objects that can help firefighters find escape routes or victims inside buildings filled with fire and smoke. This technique can also help track hypersonic objects such as rockets and space debris.

New method described in Nature Communicationscan provide important information that can help reduce death and injury. Locating and tracking indoor emergency responders is the primary goal of the public safety community. Hundreds of thousands of pieces of space debris in orbit are considered hazardous to humans and spacecraft.

“Our system allows real-time imaging around corners and through walls, as well as tracking fast moving objects such as millimeter-sized space debris flying at 10 kilometers per second, over 20,000 miles per hour, all from a remote location. distances, ”said physicist Fabio. da Silva, who led the development of the system while at NIST.


This demonstration of the m-Widar (Microwave Image Detection, Analysis and Ranging) system shows the video on the left of a person walking and then crouching and lying in an anechoic chamber. The transmitters and receiver are located in a vertical line on the right side of the camera. The second video from the right shows an image of the same scene from the instrument. Approximately 21 seconds after the start of the video, a wall panel is inserted between the person and the instrument in the anechoic chamber to show that m-Widar can “see” through the walls. Credit: NIST

“Since we use radio signals, they pass through almost everything, such as concrete, drywall, wood and glass,” added da Silva. “It’s pretty cool because not only can we peer behind walls, but it only takes a few microseconds of data to frame an image. Sampling is happening at the speed of light, as fast as physically possible. “

The NIST imaging method is a form of radar that sends out an electromagnetic pulse, waits for reflections, and measures round trip times to determine the distance to a target. Multi-position radar typically has one transmitter and multiple receivers that pick up echoes and triangulate them to determine the location of an object.

“We used the concept of a multi-site radar, but in our case we are using many transmitters and one receiver,” said da Silva. “This way we can find and display anything that is reflected anywhere in space.”

Da Silva explains the rendering process as follows:

“To imagine a building, the actual volume of interest is much smaller than the volume of the building itself, because it is basically an empty space with rare objects in it. To find a person, you need to divide the building into a matrix of cubes. Typically, you transmit radio signals to each cube individually and analyze the reflections, which is very time-consuming. In contrast, the NIST method checks all cubes at the same time and uses echoes from, say, 10 out of 100 cubes to compute where the person is. All transmissions will return an image, while the signals form a pattern, and empty cubes fall out. “

Da Silva applied for a patent and recently left NIST to commercialize a system called m-Widar (Microwave Image Detection, Analysis and Ranking) through a new company, Wavsens LLC (Westminster, Colorado).

The NIST team demonstrated this technique in an anechoic (anechoic) chamber, capturing images of a three-dimensional scene in which a person moves behind drywall. The transmitter power was equivalent to 12 mobile phones simultaneously sending signals to create images of a target from a distance of about 10 meters (30 feet) through a wallboard.

Da Silva said the current system has a potential range of up to several kilometers. With some improvements, he said, the range could be much larger, limited only by transmitter power and receiver sensitivity.

The underlying technique is a form of computational rendering known as transient rendering, which has been used as an image reconstruction tool since 2008. The idea is to use a small sample of signal measurements to reconstruct images based on random patterns and correlations. This technique has been previously used in communication coding and network management, machine learning, and some advanced forms of visualization.

Da Silva combined signal processing and simulation techniques from other fields to create a new mathematical formula for image reconstruction. Each transmitter simultaneously emits different pulse patterns in a specific random sequence, which interfere in space and time with pulses from other transmitters and produce enough information to generate an image.

The transmitting antennas operated at frequencies from 200 megahertz to 10 gigahertz, roughly in the upper half of the radio frequency spectrum, which includes microwaves. The receiver consisted of two antennas connected to a signal digitizer. The digitized data was transferred to a laptop and loaded into a graphics processor for image recovery.

The NIST team used this technique to reconstruct a scene with 1.5 billion samples per second, which equates to an image frame rate of 366 kilohertz (frames per second). For comparison, this is about 100-1000 times more frames per second than a mobile phone camcorder.

Using 12 antennas, the NIST system generated 4096-pixel images with a resolution of about 10 centimeters on a 10-meter stage. This image resolution can be useful when privacy or confidentiality is important. However, resolution can be improved by upgrading the system with existing technology, including more transmit antennas and faster random signal generators and digitizers.

In the future, images can be improved with quantum entanglement, in which the properties of individual radio signals become intertwined. Entanglement can improve sensitivity. RF quantum illumination circuits can increase reception sensitivity.

The new imaging technique could also be adapted to transmit visible light instead of radio signals – ultrafast lasers can improve image resolution but lose the ability to penetrate walls – or the sound waves used for sonar and ultrasound imaging.

In addition to capturing images of emergencies and space debris, da Silva said the new method could also be used to measure the speed of shock waves, a key metric for evaluating explosives, as well as tracking vital signs such as heart rate and respiration.

Reference: “Continuous Microwave Imaging” by Fabio C.S. da Silva, Anthony B. Cos, Grace E. Antonucci, Jason B. Coder, Craig W. Nelson and Archita Hati, June 25, 2021, Nature Communications
DOI: 10.1038 / s41467-021-24219-0

This work was funded in part by the Public Safety Trust Fund, which provides funding to NIST organizations leveraging NIST’s communications, cybersecurity, manufacturing, and sensor expertise to research critical, life-saving technologies for first responders.





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Farming robots are the future – we must prepare now to avoid dystopia

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Dystopian Farm Robots


This illustration shows the scenario of a utopian farming robot. Credit: Natalis Lorenz.

This is no longer science fiction, farm robots are already here – and they have created two possible extremes for the future of agriculture and its impact on the environment, says agricultural economist Thomas Daum in an article published July 13, 2021 in Science & Society. Journal Trends in ecology and evolution… One of them is a utopia, in which entire parks of small intelligent robots work in harmony with nature to produce a variety of organic crops. Another is a dystopia in which large, tractor-like robots conquer the landscape with heavy machinery and artificial chemicals.

He describes the utopian scenario as a mosaic of rich green fields, streams, wild flora and fauna, where fleets of small robots powered by sustained energy flutter around the fields, their buzzing mingling with the chirping of insects and the song of birds. “It’s like a Garden of Eden,” says Daum (@ThomDaum), a research associate at the University of Hohenheim in Germany who studies agricultural development strategies. “Small robots can help conserve biodiversity and combat climate change in ways that have never been possible before.”

He suggests that a utopian scenario that is too laborious for conventional farming, but possible with robots working around the clock, 7 days a week, is likely to benefit the environment in many ways. Plants would be more varied and the soil richer in nutrients. Thanks to micro-spraying of biopesticides and laser weed removal, nearby water, insect populations and soil bacteria will also become healthier. Organic crop yields, which are now often lower than traditional crop yields, will be higher and the impact of agriculture on the environment will be greatly reduced.

Dystopian farm robots

This illustration shows the scenario of a dystopian farming robot. Credit: Natalis Lorenz.

However, he believes that a parallel future with negative environmental consequences is quite possible. In this scenario, he says, large but technologically crude robots will bulldoze the natural landscape, and multiple monocultural cultures will dominate the landscape. Large fences would isolate people, farms and wildlife from each other. Once people are removed from farms, agrochemicals and pesticides can be used more widely. The ultimate goals will be structure and control: qualities that these simpler robots excel at, but which are likely to have detrimental effects on the environment.

While he notes that it’s unlikely the future will be limited to pure utopia or pure dystopia, by creating these two scenarios, Daum hopes to spark a conversation in what he sees as a crossroads in time. “Both utopia and dystopia are possible from a technological point of view. But without the right policy barriers, we could end up in a dystopia without even wanting to, if we don’t discuss it now, ”says Daum.

But this impact is not just limited to the environment – it affects normal people as well. “Robotic farming can also specifically impact you as a consumer,” he says. “In utopia, we don’t just grow crops – we have a lot of fruits and vegetables, the relative prices of which will fall, so a healthier diet will become more affordable.”

The small robots described in Daum’s utopian scenario would also be more suitable for small farmers who would find it easier to afford or share them through services like Uber. On the contrary, he argues that a family farm is less likely to survive in a dystopian scenario: only large producers, he says, will be able to manage huge tracts of land and high costs for large machinery.

In parts of Europe, Asia and Africa, where there are currently many small farms, deliberate efforts to implement a utopian scenario offer clear advantages. The situation is more difficult in countries such as the United States, Russia or Brazil, which have historically been dominated by large farms producing large volumes of low-value grains and oilseeds. There, small robots that are less efficient at performing energy-intensive tasks like threshing corn may not always be the most cost-effective option.

“While it is true that the preconditions for small robots are more complex in these areas,” he says, “even with large robots – or a mixture of small and large ones – we can take steps towards utopia with practices like interbreeding, having hedges. agroforestry and the shift from large farms to smaller plots of land owned by large farmers. Some of these methods may even pay off to farmers when robots can do their job as previously unprofitable methods become profitable. ”

To do this, Daum said, you need to act now. While some aspects of the utopian scenario, such as laser weeding, are already developed and ready for widespread adoption, funding must go to other aspects of machine learning and artificial intelligence in order to develop robots intelligent enough to adapt to complex unstructured farming systems. Policy changes are also needed and can take the form of subsidies, regulations, or taxes. “In the European Union, for example, farmers receive money when they perform certain landscape services, such as growing many trees or rivers on their farms,” he says.

While it may seem like a dystopian scenario is more likely, it is not the only way forward. “I think utopia is achievable,” says Daum. “It won’t be as easy as a dystopia, but it’s quite possible.”

Link: “Farming robots: ecological utopia or dystopia?” Thomas Daum, July 13, 2021 Trends in ecology and evolution
DOI: 10.1016 / j.tree.2021.06.002

This work was supported by the “Companion Research Program for Agricultural Innovation”, which is funded by the German Federal Ministry for Economic Cooperation and Development (BMZ).





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Dynamic control of THz wavefronts due to rotation of layers of cascade metasurfaces

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Metadevice for Dynamically Controlling THz Wavefronts


Meta-device for dynamic control of THz wavefronts by rotating layers of cascade metasurfaces. Credit: Shanghai University.

Cascading metasurfaces for dynamic control of THz wave fronts

Electromagnetic (EM) waves in terahertz (THz) mode are used for critical applications in communications, security imaging, and bio and chemical sensing. This widespread applicability has led to significant technological progress. However, due to the weak interaction between natural materials and THz waves, conventional THz devices are usually cumbersome and ineffective. Although ultra-compact active devices in the THz range do exist, modern electronic and photonic approaches to dynamic control are ineffective.

Recently, the rapid development of metasurfaces has opened up new opportunities for creating highly efficient ultra-compact devices in the THz range for dynamic wavefront control. Ultra-thin metamaterials formed by subwavelength planar microstructures (i.e., metaatoms), metasurfaces allow tuning optical responses to control the fronts of electromagnetic waves. By creating metasurfaces that have certain predefined phase profiles for transmitted or reflected waves, scientists have demonstrated exciting wave manipulation effects such as abnormal light deflection, polarization manipulation, photon spin hall and holograms.

Dynamic beam steering metaservice

Demonstration of the dynamic beam steering meta-device: (a) Schematic of the meta-device, which consists of two layers of transmissive metasurfaces aligned with a motorized turntable. (b) top view (left) and (c) bottom view (right) of a SEM image of the fabricated meta-device. (d) Diagram of the experimental setup shown to characterize the meta-device. (e) Experimental and (f) simulated far-field scattering power distribution with a meta device illuminated with 0.7 THz LCP light and evolving along path I at different times. (g) Evolution of the directions of the transmitted waves on the sphere of direction k when the meta device moves along Path I and Path II, with the solid line (asterisks) denoting the results of the simulation (experiment). Here, the blue area denotes the solid angle for beam steering coverage. Credit: X. Cai et al., Doi 10.1117 / 1.AP.3.3.036003.

Moreover, the integration of active elements with individual meta-atoms within passive metasurfaces allows the creation of “active” meta-devices that can dynamically manipulate the fronts of electromagnetic waves. While active elements in deep subwavelengths are easy to find in microwave mode (e.g. PIN diodes and varactors) and successfully contribute to active meta-devices for beam steering, programmable holograms, and dynamic imaging, they are difficult to create at frequencies above THz. … This difficulty stems from size limitations and significant ohmic losses in electronic circuits. Although terahertz frequencies can drive terahertz beams uniformly, they usually cannot dynamically manipulate terahertz wave fronts. Ultimately this is due to the lack of local tuning capabilities at subwavelength depth scales in this frequency domain. Therefore, developing new approaches to avoid local customization is a priority.

As reported in Advanced PhotonicsResearchers from Shanghai University and Fudan University have developed a general structure and meta-devices to achieve dynamic control of THz wave fronts. Instead of locally controlling individual meta-atoms in the THz metasurface (for example, via a PIN diode, varactor, etc.), They change the polarization of the light beam using rotating multilayer cascade metasurfaces. They demonstrate that rotating different layers (each exhibiting a specific phase profile) in a cascade meta-device at different speeds can dynamically change the effective Jones matrix property of the entire device, achieving unusual manipulations with the wavefront and polarization characteristics of terahertz rays. Two meta-devices are demonstrated: the first meta-device can effectively redirect a normally incident THz beam for scanning in a wide range of solid angles, and the second can dynamically manipulate both the wavefront and polarization of the THz beam.

This paper proposes an attractive alternative way to achieve inexpensive dynamic control of THz waves. The researchers hope this work will inspire future applications of terahertz radars as well as bio and chemical sensing and imaging.

Reference: “Dynamic control of terahertz wavefronts with cascading metasurfaces” Xiaodong Tsai, Rong Tang, Haoyang Zhou, Qiushi Li, Shaoji Ma, Dongyi Wang, Tong Liu, Xiaohui Lin, Wei Tang, Qiong He, Shii Xiao, and Lei Zhou, June 26 … 2021, Advanced Photonics
DOI: 10.1117 / 1.AP.3.3.036003





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Take part in ESA Space Camp 2021

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Take part in ESA Space Camp 2021


Space App Camp 2021. Credit: ESA.

ESA invites up to 25 dedicated mobile app developers and AI and machine learning specialists related to Earth observation from space to join this year’s Space App Camp, which will be a virtual event for eight weeks, from July 20 to September 20. …

The Space App Camp aims to make Earth observation data and services available to a wide range of citizens using their smartphones or personal devices. Numerous Earth observation satellites, including Copernicus Sentinel missions, collect a huge amount of data. This big data from space uncovers information about the atmosphere, land and water of our planet and offers countless possibilities for creating compelling, even transformative applications when combined with mobile applications.

Space App Camp attendees will experience Copernicus data and learn how big data from space can enrich mobile apps with a dedicated Earth observation data API. The 2021 virtual edition revolves around an expanded collaboration with ESA’s F-Lab, whose mission is to accelerate future Earth observation through new transformational ideas, and to select, develop, test and develop the most promising concepts.

2020 space camp winner

Quifer (aQuifer sUrveillance by sentInel InterFERometry) won the top prize in Space App Camp 2020. It uses terrain data from the Copernicus Sentinel-1 mission, combined with big data and artificial intelligence to monitor water use. Credit: ESA.

Although this is the tenth Space app campThis is the first time the camp has offered an expanded mentoring program that includes an end-to-end training and mobile software development scheme lasting eight weeks, supported by experts in Earth observation, artificial intelligence, intellectual property protection and business. development.

Winners will be awarded cash prizes of up to € 2,500 and a unique Earth observation support package that will allow them to continue working on their winning app idea. They will also be invited to participate in ESA exhibitions. Φ-week and Living Planet Symposium, with all expenses covered.

There is also a unique prize in the form of an Earth Observation Support Package worth around € 3,500. This includes technical advice on Earth observation data, eight hours of software development services, access to a global network of Earth observation experts in application and technical fields, and support from professional ESA business developers.

Carlos Garcia, member of the 2020 winning team, says: “The ESA Space App Camp is a great opportunity to build an app from scratch with guidance from tier 1 professionals. Although everything was virtual in my year, it was a fantastic learning experience – blocking the week and dedicating myself to building a meaningful app. “

The deadline for applications is July 8, 2021. Interested students, entrepreneurs, researchers, developers, and economists can register online individually or in a team (up to four people). This year’s edition is specifically targeted at contributors with profiles in mobile app development, Earth observation app development, machine learning, artificial intelligence, and business development.

To participate in the 8-week mentoring program from July 20 to September 20, 2021, up to 25 participants will be selected, within which special training and development sessions will be held every two weeks.

Since Space App Camp was created 10 years ago, about 480 developers from 30 countries have applied to participate and more than 60 applications have been developed. Some of them have already found use in commercially viable applications.





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