Ph.D. Proposal Defense  
Candidate: Nikolaus Lehmann
Advisor: Prof. Alexander M. Haimovich
Date: April 27, 2006 (Thursday)
Time: 10:00 am
202 ECE, NJIT

Title: Fundamentals of MIMO-Radar

Abstract:

Motivated by recent advances in MIMO wireless communications, this proposal aims at exploring the potential of MIMO approaches in the radar context. In communications,MIMO systems combat the fading effects of the multi-path channel with spatial diversity.

Further, the scattering environment can be used by such systems to achieve spatial multiplexing. In radar, the complex targets consisting of several scatterers take the place of the multi-path channel. A target’s radar cross section (RCS), which determines the amount of returned power, greatly varies with the considered aspect. Those variations significantly impair the detection and estimation performance of conventional radar employing closely spaced arrays on the transmit and receive side. In contrast, by widely separating the transmit and receive elements, MIMO-radar systems observe a target simultaneously from different aspects resulting in spatial diversity. This diversity overcomes the fluctuations in received power. Similar to the multiplexing gain in communications, the simultaneous observation of a target from several perspectives enables to resolve its properties with an accuracy beyond the one supported by the bandwidth. The proposal studies the MIMO concept in radar in the following manner. First, angle of arrival estimation with a system applying transmit diversity on the transmit side is explored. Due to the target’s RCS fluctuations, the notion of ergodic and outage Cramer Rao bounds is introduced. Both bounds are compared with simulation results revealing the potential of MIMO-radar. Afterwards, the detection of targets in white Gaussian noise is discussed including geometric considerations due to the wide spacing between the system elements. The detection performance of MIMO-radar is then compared to the one achieved by conventional phased array radar systems. Some important general conclusions are derived from this comparison. The discussion is then extended to include returns from homogeneous clutter. A Doppler processing based moving target detector for MIMO radar is developed in this context. Based on this detector, the moving target detection capabilities of MIMO-radar are evaluated and compared to the ones of phased array and multi-static radar systems. It is shown, that MIMO-radar is capable of reliably detecting targets moving in an arbitrary direction. Finally, the high resolution capabilities of MIMO-radar are explored. As noted above, the several individual scatterers constituting a target result in its fluctuating RCS. The high resolution mode is aimed at resolving those scatterers. Therefore, it is first explored how observing a single isotropic scatterer from several aspects enhances the accuracy of estimating the location of this scatterer. This leads to a new, two-dimensional ambiguity function. This ambiguity function is used to illustrate that several scatterers can be resolved within a resolution cell given by the bandwidth.