Researchers have found a way to use microwave frequencies to see through walls.

A recent study published in the journal Optica explains how researchers from the Duke University devised a way to see through walls by using a narrow band of microwave frequencies. What makes this new approach significant is that it enables seeing through walls even if their material composition is unknown.

Just imagine how this new technology could revolutionize our current state of security. While such tech is nothing new, especially in the fields of intelligence surveillance and military, using smaller frequencies can lower the cost of developing devices beneficial in other industries like construction.

“Most technologies that can see through walls use a broad range of frequencies, which makes them expensive. They also don’t have very good resolution. So while they might be fine for seeing a person moving on the other side of a wall, they’re terrible for finding thin conduits or wires,” says Daniel Marks, an associate research professor of electrical and computer engineering at Duke University.

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How Microwave Frequencies can be Used to see Through Walls

Existing methods that enable experts to see through walls typically require knowing the kind of components used to build the walls. This helps in determining the frequency range suitable to penetrate the walls and to separate the echoes and distortions from the solid objects being sought.

Take for example the RANGE-R device used by FBI in hostage-rescue missions and by firefighters in locating people beneath collapsed buildings during calamities. RANGE-R is equipped with what its manufacturer calls Through-the-Wall Sensors (TTWS). These sensors let anyone to see targets behind walls with the help of radio waves.

TTWS radar operates in between 1 to 10 GHz frequencies. In essence, the higher the frequency, the more accurate RANGE-R can measure the size and distance of objects behind any wall. However, the frequencies have to be adjusted depending on the wall materials because there are materials that can absorb radio waves.

Radar used by FBI and US Marshalls to see through walls
Radar used by FBI and US Marshalls to see through walls | Engadget |

While RANGE-R is no longer exclusive to the police, FBI, and military, you can only have one for a staggering $6,000 USD. The issue with wall materials and the cost of developing the device are apparently what Marks and his colleagues David Smith and Okan Yurduseven wanted to address.

Since walls are generally constructed flat in all direction, they tend to distort waves symmetrically. In their paper, Marks and his team took advantage of this symmetry.

“We wrote an algorithm that separates the data into parts—one that shows circular symmetry and another that doesn’t,” Yurduseven, a postdoctoral researcher in electrical and computer engineering at Duke, explained. “The data that doesn’t have any symmetry is what we’re trying to see.”

The researchers only utilized a narrow band of microwave frequencies to scan walls because it cuts down on the number of interference patterns created by the wall. Aside from that, single-frequency emitters are said to be less expensive than broadband emitters.

Furthermore, narrow range frequencies will enable future devices to be quickly cleared by the Federal Communications Commission (FCC) because they won’t spark conflicts with other technologies using microwave frequencies such as WiFi, mobile phones, and Bluetooth.

In their laboratory, the researchers built a prototype device to test their new method. They used it to scan different kinds of walls they constructed themselves. Objects that workers might want to find like studs, electrical conduits, wires, and junction boxes were placed behind the walls.

Raw data taken after scanning a wall using a narrow band of microwave frequencies
Raw data taken after scanning a wall using a narrow band of microwave frequencies | Daniel Marks | Duke University

The data gathered from the scanning procedure yielded some satisfying results, especially after removing the symmetrical patterns. The researchers were able to recognize the individual objects because they appear considerably clear.

“We envision combining this technique with a machine vision system that someone could move over a wall to see what’s inside,” Marks went on to say. “We think the technology has the price point and sensitivity to make an impact on the market.”

Do you agree with having devices that can see through walls commercially available in the market at an affordable price?

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