Making radar more accurate

Synchronizing radar antennae provides powerful military security.

Professor Hongbin Li of Electrical Engineering Graduate and Undergraduate Degree ProgramsDr. Hongbin Li, Professor of Electrical Engineering at Stevens Institute of Technology, has recently been awarded a three-year US Air Force Research Laboratory (AFRL) contract to study distributed radar systems and improve object detection. His research will develop networked radar capabilities that are turning today's "moving object detectors" into tomorrow's precision imaging systems.

"As director of the Signal Processing and Communications Laboratory, Professor Li is attracting high-profile research partners and motivated graduate students to Stevens," reports Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. "Alumni of the lab that participate in his research initiatives go on to have success in industry, government, and academic careers."

Dr. Li conducted his initial research as part of the Air Force Office of Scientific Research (AFOSR) Summer Faculty Fellowship Program in 2009. After seeing the preliminary results, Dr. Li's technical director encouraged him to apply for the contract.

Dr. Li's research addresses the problems inherent in traditional, monostatic phased-array radar. Multiple antennae transmit and receive signals from a single site, leaving objects that move tangentially to the receivers essentially invisible. Even when objects are sensed by radar, their particular geometry to the unit can produce a wide range of signal strengths, making it difficult to positively identify the object in strong clutter.

To address these obstacles, Dr. Li is using the lessons of multiple-input and multiple output (MIMO) technologies to support interlinked radar units capable of producing images with better resolution and accuracy. Although MIMO has a broad background literature and is a trending subject in wireless communications, MIMO radar is relatively new. To enable MIMO capability in radar, Dr. Li is applying the lessons of signal processing to connect data incoming from multiple sources.

"This is really fundamental research into signal processing," says Dr. Li. "In this case, the sensors generating signal are radar units. Signal processing algorithms are needed to get the radar to synchronize and cooperate."

The many difficulties of networked communications are amplified in MIMO radar applications. Multiple spatially distributed radar transmitters produce signals that are not synchronized, creating significant difficulties for separation at the receivers, and potential interference must be taken into account. The unique images captured by distributed radar placements require reconciliation to produce a single, coherent image. Radar must also deal with a large amount of "clutter," the fixed objects in a landscape that often produce stronger signals than targets of interest.

As part of facilitating networked MIMO radar, Dr. Li is also addressing how to get all this data communicated efficiently.

"For imaging applications, higher resolution is obviously better," says Dr. Li. "While traditional techniques rely on increasing bandwidth for higher resolution, the MIMO radar approach affords higher spatial resolution through the use of a distributed sensing aperture. Our goal is to combine software and hardware that can get the best bandwidth from multiple radar sensors."

In the lab at Stevens, Dr. Li will work with electrical engineering Ph.D. candidates to develop new algorithms and run computer simulations of their mathematical models of MIMO radar. This will be Dr. Li's second contract with AFRL. His first, a five-year contract, ended late last year.

"The use of MIMO in radar and other sensing applications is expected to be widespread in the near future," says Dr. Yu-Dong Yao, Director of the Department of Electrical and Computer Engineering. "This contract will significantly enhance research into this important field and provide many opportunities for student and faculty development at Stevens."