Researchers Take Inspiration From Superman’s X-Ray Vision for Imaging Chip

Researchers from the University of Texas at Dallas (UTD) recently demonstrated a lens-less, reflection-mode radar imaging chip using a commercial CMOS process. This chip, operating with a frequency range of over 100 GHz, can image obscured targets for many different applications.

 

UTD researchers developed a radar imaging chip that can detect obscured targets using mmWave radar. 

 

Radar has evolved considerably since its conception over 100 years ago, and, thanks to modern semiconductor advancements, can operate at higher frequencies. These higher frequencies help with spectrum congestion and competition while also yielding better imaging devices in smaller packages. The UTD radar imaging chip leans on the ability of electromagnetic (EM) waves to penetrate opaque objects, pushing imaging technology one step closer to seeing through walls.

The researchers drew inspiration from Superman's X-ray vision—except, instead of using actual X-ray technology, which can be harmful to humans, the team used signals at 200 GHz to 400 GHz. This technology, refined over 15 years of research and combined with digital signal processing techniques, provides a glimpse into the potential of true terahertz imaging. 

 

Radar Imaging Explained

Radar leverages EM or radio waves to precisely measure motions or distances using invisible energy. Both radio and visible light waves are fundamentally equivalent, meaning that a radar system using multiple receivers and a lens could readily image its surroundings to provide a new perspective on the environment. 

Practically, however, radio waves have a much longer wavelength (>1,000× larger than optical), meaning that lenses and receivers can be much larger than their optical counterparts. As a result, a lens-less receiver array operating at a high frequency can negate the need for bulky components.

 

The UTD radar imaging chip uses three collocated pixels to image the environment, along with several active components on-chip to create the radiated, high-frequency signal. 

 

This is exactly what the UTD radar imaging chip aims to accomplish. The chip uses an array of 300-GHz receivers along with an accompanying transmitter to illuminate and detect targets. This detection, coupled with advanced signal processing, converts the output to an image, opening doors to manifold applications in security, defense, or automotive designs.

 

Dipping to Sub-mm Frequencies

While high frequencies offer many benefits, it's not always practical to generate or distribute a signal on the order of 300 GHz. To address this, the UTD team used a novel architecture that begins with a lower frequency before ultimately working up to the final mmWave frequency.

 

Block diagram of the system in its imaging mode. 

 

The UTD chip's transmitter used an externally provided signal source at approximately 24 GHz to ensure low losses in PCB traces. This signal was then doubled, tripled, and doubled again on the chip to create the final signal radiated at approximately 296 GHz (λ ≈ 1 mm). This signal was then scattered in the environment, and its reflections were collected at a receiver array.

 

The UTD imaging chip accurately imaged hidden devices in high resolution. 

 

On the receiver side, three pixels collect the reflected signal and downconvert it to a much more PCB-friendly 9 MHz, with amplification along the way. Then, using advanced signal processing techniques, the output can be converted to an image showing key features of the scene. In a variety of tests, the UTD team demonstrated that the simple device can show features of an object that would normally be obscured to the human eye.

 

Handheld X-Ray Vision to Come? 

A primary concern with this technology is privacy, and rightfully so. The UTD team has designed the chip to be used approximately one inch from a target. This ensures that bad actors cannot use this technology in a public space without being detected by their proximity. When integrated into a cellphone, however, this technology could have many useful applications. Users could detect studs behind a wall, peek into packages or envelopes, or even peer into their own bodies to gather health information.

While this technology may not be readily available to the public anytime soon, the UTD team believes its prototype represents a significant leap in high-frequency imaging techniques. Developed further, this radar imaging chip may one day allow users to visualize their environment without reliance on visible light.

 

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All images used courtesy of UTD.