SAM 2012 - Plenary Speakers
Advances in Waveform Scheduling for MIMO Radar
Abstract: In a MIMO active sensing systems, different waveforms are transmitted simultaneously from different emitters and the returns are processed to detect targets and to also determine their speed and location. A major challenge in MIMO radar is waveform separation at the receiver. The relative delays and doppler shifts of the superimposed echoes greatly diminish the efficacy of employing orthogonal waveforms. Novel transmit waveform matrices will be presented that dictate the scheduling of complementary waveforms over both multiple Pulse Repetition Intervals (PRIs) and multiple emitters. The designs also dictate the matchedfiltering done over multiple PRIs at the different receivers. The diverse waveform matrix designs are quite remarkable in that when one sums the running matched-filter outputs over multiple PRIs at a given receiver, one achieves the delta function effect (at each true target delay) relative to the waveforms sent from a particular transmit antenna, while simultaneously canceling the contributions from the other transmit antennas. The challenge is to design such waveform matrices under a unimodular constraint on the sequence values due to the nonlinear amplifiers employed in radar for power efficiency.
Initial proof-of-concept simulation results have centered on a 4x4 system which, for example, may be realized as four beams transmitting different waveforms simultaneously, pointed to slightly different azimuth and elevation angles. The 4x4 unitary waveform matrix design dictates the scheduling of 4-ary complementary waveforms over both four transmitting beams and four PRIs. The per-element conjugation, time-reversal, and transpose of the waveform matrix dictates the matched filtering of the returns at each of four PRIs and the subsequent combining so as to achieve both perfect separation (of the superimposed returns) AND perfect reconstruction. Perfect reconstruction implies that the sum of the time-autocorrelations associated with each of the four waveforms is a delta function. Conditions for both perfect separation and perfect reconstruction have been formulated, and a variety of unitary waveform matrix designs have been formulated. The net result of the processing of four PRIs over four receivers yields sixteen cross-correlations all of which ideally exhibit a sharp peak at each true target delay.
Simulation results will be presented demonstrating the efficacy of the overall scheme, including how to exploit Doppler for enhanced resolution.
Biography: Michael D. Zoltowski is the ''Thomas J. and Wendy Engibous Professor of Electrical and Computer Engineering" at Purdue University. He is the recipient of the 2002 Technical Achievement Award from the IEEE Signal Processing Society. In addition, he served as a 2003 Distinguished Lecturer for the IEEE Signal Processing Society. He is a Fellow of IEEE. He is also a recipient of the 2006 Distinguished Alumni Award from Drexel University.
Dr. Zoltowski is a co-recipient of the IEEE Communications Society 2001 Leonard G. Abraham Prize Paper Award in the Field of Communications Systems. He is also the recipient of the IEEE Signal Processing Society's 1991 Paper Award, "The Fred Ellersick MILCOM Award for Best Paper in the Unclassified Technical Program" at the 1998 IEEE Military Communications Conference, and a Best Paper Award at the 2000 IEEE International Symposium on Spread Spectrum Techniques and Applications.
He was Technical Chair for the 2006 IEEE Sensor Array and Multichannel Workshop. He served as Vice-President for Awards and Membership for the IEEE Signal Processing Society, for 2008-2010.