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To understand Brian Rigling's work in waveform diversity, first picture a group of people in a room. Then ask yourself, "How can different groups have conversations without getting in the way of each other?" Perhaps they take turns talking (time multiplexing), speak in a high or low voice (frequency multiplexing), or speak a different language (code multiplexing).

Similar problems arise in the radio frequency (RF) spectrum, with commercial radio and TV, wireless communications, and radar all competing for airtime and spectrum. Waveform diversity researchers have developed sophisticated mathematics and intelligent algorithms to address these issues. However, can these methods be realized in practice?

To answer this question, Rigling, an assistant professor of electrical engineering in the College of Engineering and Computer Science, has collaborated with a local company to develop simulations of real hardware components in order to test the algorithms and the theory constructed by waveform diversity researchers.

"Can real hardware that we can build actually implement the sophisticated waveforms that they claim will give the improved performance?" Rigling asked. "When you use real hardware to build a system, it's going to have imperfections. Is your algorithm robust enough to survive a hardware implementation with all of its imperfections?"

Rigling's work has applications in academic, military, and industrial arenas. His research interests include sensor signal processing, which includes synthetic aperture radar (SAR), radar that uses special signal processing to produce high-resolution images of the surface of the Earth or another object while transversing a considerable flight path. SAR is extremely valuable in both military and civil remote-sensing applications. It provides surface mapping regardless of darkness or weather conditions that hamper other methods.

For the Air Force, Rigling is researching methods for radar imaging of the ground and methods for automatic recognition of targets in those images. Both of these problems require an understanding of electromagnetic scattering, or in other words, what happens when radio waves bounce off things.

To help understand how radio frequencies interact with their environment, or how radar interacts with its target, Rigling developed software for high-frequency prediction of electromagnetic scattering that he calls the Raider Tracer. Raider Tracer uses individual facets to represent three-dimensional objects, and its shooting and bouncing rays simulate how radar would respond to that object. It gives researchers access to a wealth of data that might otherwise be inaccessible due to expense or security restrictions.

Though similar software packages exist, they can be company proprietary or may have limited availability due to government restrictions. Raider Tracer acts as a kind of beta test for other researchers. While trying to obtain access permission for one of the government-restricted simulations, Rigling began developing the Raider Tracer. He wanted software that would be available to all.

"In the time I was waiting to get through all of those hoops, I wrote my own software," he said. "Neither industry or government has ownership of it, so I can post it on my Web site for anyone to use."

In partnership with the Air Force Research Laboratory, Rigling and his collaborators in the Department of Electrical Engineering received $1 million in funding to study Sensor Aided Vigilance, or SAVig. People can keep an eye on things by using video monitors, but sensors can hear and detect abnormalities at longer range and with greater persistence than the camera and human eye can see.

The idea behind SAVig is to detect abnormal activities. If a large truck stops in front of a building, and the driver gets out and runs away, then something is probably amiss.

"Can we have sensors watching a road all the time to try and detect when someone may pose a threat?" Rigling asked.

For four years prior to joining the Wright State faculty in 2004, Rigling was a systems engineer for Northrop Grumman Electronic Systems in Baltimore. He worked on synthetic aperture projects for sonar, radar, and ladar. Rigling led a team of engineers in several internal research and development efforts involving SAR. His team investigated, designed, and developed signal-processing algorithms for SAR autofocus, SAR image speckle reduction, multi-look processing, and SAR image formation.