Driving automotive radar design forward

Posted: January 2, 2020

Sophisticated navigation and collision-avoidance radars have become standard equipment in modern vehicles, saving countless lives and ushering in unprecedented safety features by enabling technologies like automatic braking, blind-spot detection and lane-change assistance.

At Ohio State’s ElectroScience Laboratory (ESL), engineers are advancing automotive radar design to improve its efficiency and effectiveness.

The research team stands behind measurement equipment in the HELIOS laboratory.
Research team members (from left) PhD student Lucas Newton, Prof. Niru K. Nahar, PhD student Maruf Hossain and Prof. Kubilay Sertel in the HELIOS Lab.

When auto-electronics manufacturer Alps Electric, the North American branch of global brand Alps Company, needed expertise to boost the performance of their millimeter-wave automotive radar, they turned to Research Assistant Professor Niru K. Nahar at the ElectroScience Laboratory.

“The synergy between the two organizations have been amazing. Ohio State has had significant contribution in advancing our projects—both in the result of their research and the measurements being conducted by their lab,” said John Cabigao, engineering manager at Alps Electric. “The support from Dr. Nahar’s team has made a significant impact on our goal. We are looking forward to further collaboration with the ElectroScience Lab and Dr. Nahar’s team in the future.”

Since 2017, the company has awarded Nahar and her team $565,000 in research funding and grants to improve their automotive antenna array and the radome that protects it—a plastic box in this instance. Together, the radar module sits directly behind the front bumper of a vehicle, which can also decrease signal strength.

“That box was very reflective with the antenna array behind it, which degrades the signal,” Nahar explained. “So even though we started with the antenna array, we ended up doing more radome work for the first year and a half.”

The research team for the project includes co-principal investigator Kubilay Sertel, associate professor of electrical and computer engineering; PhD students Maruf Hossain and Lucas Newton, post-doctoral researcher Burak Ozbey and alumnus Syed An Nazmus Saqueb ’19.

Robust radomes that don’t interfere a radar’s signal are indispensable because they can withstand adverse environmental conditions and protect the radar’s intricate circuitry.

“You have to have a strong signal,” Nahar said. “If the signal is not good, sometimes the radar won’t see the target. Or you might have a false positive—the car is going to tell you it is seeing something, but there’s nothing.”

In order to decrease signal-degrading reflections off the radome’s flat plastic sides, the Buckeye engineers suggested adding a repeating inverted pyramid texture to the plastic. Measuring less than one millimeter high, it reduces reflections and boosts the radar signal. The new radome is also wide-angle, allowing up to 90 degrees of transmission.

“We made a periodic structure on it,” Nahar said. “And that gave them a much better transmission level covering the whole automotive frequency band.”

After performing modeling and simulation of the new radome, the researchers 3D-printed and tested a proof-of-concept model.

The team then turned their attention to the antenna array for the radar itself. Using millimeter-wave technology in the 76 to 81 gigahertz band for autonomous vehicle navigation has led to smaller, cheaper automotive radar. But having multiple antennas in close proximity can also harm overall performance.

The researchers found that by changing the pattern of antennas used in the array they could further boost the radar’s signal.

“The proposed array is based on double-slot mmWave antennas that exhibit much lower mutual coupling, thus improving the overall field of view and performance of the radar,” Nahar explained. “We have just filled for a second patent application on the innovative antenna array design.” 

The team’s work is enabled by Ohio State’s Hyperspectral Engine Lab for Integrated Optical Systems (HELIOS), which focuses on developing faster, smaller and cheaper millimeter-wave and terahertz devices. HELIOS opened in 2011 with $3.5 million in support from the Ohio Third Frontier’s Wright Center for Sensor Systems Engineering. Containing $7.5 million of equipment, the lab is open to any academic or industry user.

“The facilities we have are really top-notch,” Nahar said. “We can do state-of-the-art autonomous automotive research from modeling, characterizations to prototyping easily because we have HELIOS.”

In addition to the product development work, Ohio State researchers also trained Alps engineers on newer measurement techniques and methods not commonly used in industry.

Not only is helping the company rewarding, Nahar said, but the project also provides valuable real-life learning for the students. The lessons learned are also applicable to other areas of sensing.

“It’s been fun, doing the work and solving the problems for them,” she explained. “Understanding this is important because the methods learned are transferable to many other applications, such as security, biomedical sensing and remote sensing. These are up-and-coming frequencies for 5G communications as well. It’s cost-effective and smaller.”

The project has resulted in two patents and the researchers presented their work in at the IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meetings.  

by Candi Clevenger, College of Engineering Communications, clevenger.87@osu.edu