Principles of Modern Radar - Volume 2 1891121537

CHAPTERMIMO Radar4Michael S. Davis✬✩Chapter Outline4.1 Introduction ................................................................... 1194.2 An Overview of MIMO Radar .................................................. 1214.3 The MIMO Virtual Array ........................................................ 1224.4 MIMO Radar Signal Processing ................................................ 1244.5 Waveforms for MIMO Radar ................................................... 1354.6 Applications of MIMO Radar .................................................... 1384.7 Summary ...................................................................... 1424.8 Further Reading ............................................................... 1434.9 References .................................................................... 1434.10 Problems ...................................................................... 145✫✪4.1 INTRODUCTIONRadar systems have long used multiple antennas on receive to increase performance, butthe idea of using multiple transmit antennas to emit a collection of independent waveformsis relatively new. Such a radar is called a multiple-input, multiple-output (MIMO) radarbecause it probes its environment by applying multiple inputs and observing multiple outputs.Inspired by the success of MIMO techniques at improving wireless communications,researchers have been actively investigating the potential of MIMO radar since the turn ofthe century [1].In a sense, a MIMO radar is a natural extension of the phased array antenna thathas been used by radar systems for decades [2]. A phased array consists of a number ofradiating elements. Each element transmits the same signal except that a phase shift (ortime delay) is applied so that a beam is steered in a particular direction. In a phased array,the signals transmitted from each element are perfectly correlated. A MIMO radar is ageneralization of a phased array in that the signals need not be correlated from element toelement.4.1.1 OrganizationFirst, a brief overview of the MIMO radar concept is provided. The utility of transmittingorthogonal waveforms is motivated by introducing the idea of the MIMO virtualarray. A signal processing framework is then established, which provides insight into the119