V.S. Chernyak - Dr. Sc. (Eng.), Professor, Moscow Aviation Institute and Bauman Moscow State Technical University (National Research Universities). E-mail: chernyak@mail.ru

One of the important advantages of MIMO radars with colocated antennas is the capability to exclude scanning of a surveillance sector in search mode thanks to broad transmitting beams. This is a result of orthogonal (or close to orthogonal) waveforms radiated by all elements of a transmitting antenna array. In tracking mode all these elements can radiate the same waveform forming narrow transmitting beams and concentrating radiated energy on detected targets as in a conventional phased antenna array. In recent years many publications have been appeared (mostly in foreign literature) where advantages and disadvantages of MIMO radars with colocated antennas as well as their structures and possible applications are considered. However, energy characteristics of such radars have been investigated insufficiently. It is known that radiation of orthogonal (or close to orthogonal) signals by different elements of a transmitting antenna array leads to energy loss caused by signal noncoherent summation on a target (and accordingly broad beamwidths of the array). On the other hand, in many works the possibility of loss compensation is assumed by forming narrow transmitting beams on receive. To the author knowledge, there is no sufficiently rigorous and systematic consideration of MIMO radar detection problem in available literature including possibility of either coherent or noncoherent signal transmission. Statistical synthesis of optimal detection algorithms (according to Neyman-Pearson criterion) has been carried out in the paper for MIMO radars with coherent and noncoherent mutually orthogonal transmitting signals in a background of white Gaussian noise. As a result, block diagrams for optimum detectors in search mode are obtained where target location is apriori unknown. Several structures are given with different order of linear transformations. Analysis of the synthesized algorithms and their comparison with the optimum detection algorithm for a radar with a conventional phased antenna array has revealed the specific values of energy loss for both coherent and noncoherent transmitting signals. Specifically, it has been shown to what degree narrow transmitting beams on receive can compensate for energy loss caused by the orthogonality of transmitting waveforms.