Multiple Input, Multiple Output (MIMO) technology has been on the horizon for decades now, however its full potential has not yet been leveraged for radar systems. Therefore, most of the state of the art practical radar systems are typically phased array radars and not MIMO radars. This thesis focusses on methods, techniques and implementation of multi-antenna radar systems for an improved quality of target information. Multi-static radars offer diversified degrees of freedom and arbitrary geometrical patterns that can be exploited according to the target specifications. We investigated novel signal processing algorithms for MIMO based, pulsed and frequency modulated continuous wave (FMCW) radars and prototyped some of our work using National Instruments' RF equipment. The developed algorithms were simulated using MATLAB and NI Visual System Simulator (VSS), implemented using National Instruments' software defined radios along with the performance analysis of the proposed algorithms.

This thesis studies multi-antenna systems for multitude of radar applications. It starts with the performance analysis of MIMO radar systems for fluctuating target compared to conventional monostatic radars with single antenna. A novel algorithm has been developed that makes use of spatial and temporal diversity of MIMO systems to improve the detection performance of fluctuating Swerling targets. Thereafter, this thesis focusses on the performance of multi-antenna radar systems under jamming and electronic counter measures. A novel approach for hybrid phased-MIMO radar was developed that exploited benefits of both phased array and MIMO radar and maximized the signal to noise plus jamming ratio (SNJR). Furthermore, a robust approach for mitigation of noise jamming in a linear array system was developed that makes use of sidelobe blanking along with the optimal beamforming weights of the main and auxiliary antenna arrays. The proposed approach restricts the sidelobes below a desired threshold, nullforms the jamming angles and maximizes gain in the target's direction.

Thereafter, this thesis studies synchronization of multi-antenna radar systems. A simple cost effective mechanism was developed for synchronizing widely separated distributed MIMO radar network using an open source implementation of GSM protocol stack. A method to improve the spectral efficiency of the radars have been studied next, that mixes the Barker code with the linear frequency sweep of a frequency modulated continuous wave radar. An optimal Barker sequence length that jointly optimizes the range resolution and spectral efficiency was determined. To complete this thesis, multi-antenna radar system has been implemented using National Instruments' software defined radios. Specifically, the issue of crosstalk in modern USRP based software defined radios for implementation of FMCW radar has been highlighted. Crosstalk effects in bistatic configuration are also presented. A naive approach for recovering the transmitted waveform by synchronizing multiple USRPs was developed. It is shown that dynamic range can be increased by tens of kilometers by increasing baseline distance to few inches. Finally, conclusions and future directions have been presented. In particular, design and implementation of adaptive cognitive radars has been discussed.