Researchers at the Fraunhofer Institute for Applied Solid State Physics (IAF) have developed a lightweight, compact radar that can “see” through non-transparent materials and whiteout snow conditions. The compact radar operates at frequencies of 75 to 110 GHz in the millimeter range W-band of the radio spectrum. Radars at this frequency can not only identify small objects up to three kilometers (1.8 miles) away, but they can also penetrate all manner of non-transparent, dielectric, and non-metallic materials, such as clothing, plastic surfaces, paper, wood, snow and fog.
This sort of radar has been around for a long while in military and some civilian applications, but Fraunhofer has developed a new, more compact modular design to allow it broader use. The new design is a compact radar about the size of a cigarette box with three-channel antennas with dielectric lenses and can accommodate USB and CAN-BUS interfaces.
Conventional W-band radars are largely restricted to military applications because they use ceramic substrates weighing in at up to five kilograms (11 lb) that makes them large and expensive. By using a gallium arsenide semiconductor, Fraunhofer was not only able to reduce the size and costs of the sensor, but also improve the resolution by being able to address frequencies over 100 GHz.
“In principle, our system can be compared with that of a bat. When bats emit ultrasonic signals, echoes bounce back from walls, branches, moths, and gnats. The bats use these echoes to determine what obstacles lay ahead, and the echoes allow them to distinguish between obstacles and prey. If nothing were in the way, there would be no echo. So they see with their ears,“ said Dr. Axel Hülsmann, an engineer at IAF. “Our radar emits signals that are reflected by the objects under observation. With the help of numerical algorithms, the signals transmitted and received can be compared to one another. And this comparison makes it possible to determine the distance, size, thickness, and speed of the object. If the object does not move, the signal remains unchanged.“
The compact radar module can not only generate and receive signals, it can also process digital signal traffic and contains a high-frequency module and a signal processor. It can also cover large areas, such as fences or ports. “Since we are using a dielectric antenna, the angle of aperture can be freely selected. This means recorded data can cover a close-up of large surfaces just as easily as small, far away objects,“ said Hülsmann. “When there is fog, as is often the case at Hamburg’s port on the Elbe River, security cameras are unable to deliver high-resolution images. This is why the authorities often patrol with dog units when the weather is bad.“
Fraunhofer sees the compact radar as having a wide range of applications with a particular emphasis on helicopter rescues because of the radar’s ability to see in whiteout conditions as well as providing landing support in all ambient conditions and accurate altitude/distance readings. It’s also suitable for security, medical, logistics and industrial settings.
“The W-band radar can be used in any situation where other sensor technologies in manufacturing processes have failed because of high temperatures or limited visibility. Just to name one example, it can be used as a filling level sensor in flour silos: a great deal of dust forms when they are being filled,“ said Hülsmann.
A prototype of the W-band radar is scheduled to be presented at the Hannover Messe, which runs between April 8 and 12. There, the exhibitors will demonstrate the radar’s ability to determine the level of water in two concentric tubes with the gap between them filled with fog. According to Fraunhofer, the radar will be able to detect the water level where an optical sensor would be blinded.
Fraunhofer expects an improved version of the compact radar will be on the market in two years.