Research On Space-time Optimization Designation For Airborne Cognitive MIMO Radar

The cognitive radar is a closed lopped adaptive system which has not only the adaptive receiver but also the adaptive transmitter enabled by the feedback from the receiver. MIMO radars have a higher emission degree of freedom, so the newly proposed cognitive MIMO radar has become a widely concerned radar system. This work introduces the cognitive MIMO radar principles into the airborne radar and specifically discusses the suppression problems of the colored noise and clutter with the help of theoretical derivation, modeling and simulation experiments. The main contents of this paper are as follows:1.Introduces the system framework of the airborne cognitive MIMO radar and the possibly array arrangement; Establishes the basic principles of the cognitive information acquirement as well as the space-time optimization designation problems. The clutter modeling and information extraction approaches are described in details.2. Discusses the waveform designation problem of the airborne cognitive MIMO radar systems. To maximize the SNR, several eigenvalue-based waveform designation approaches are analyzed. Specifically discusses the waveform with constant modulus within the colored noise background. The waveform optimization result of the eigenvalue-based approach is regarded as the expected waveform. Then the MIMO waveform coding is realized by the sequential quadratic programming. This approach makes full use of the degree of freedom of the emission arrays as well as the transmit power, so the output SNR can be further improved.3. The emission space-time weights designation problem of the airborne cognitive MIMO radar is studied. The emission space-time weights optimization approaches for both the phased-array radar and MIMO radar systems are introduced and simulated. For the phase-array radar systems, the space-time weights are optimized under the MVDR principle, which is able to format a filter notch in space-time pattern corresponding to the clutter edge. For the MIMO radar systems, the space-time weights optimization problem is modeled with the transmit matrix, and the optimization function is developed to maximize the SCNR. This approach can effectively suppress the clutter. Besides that, the dynamic range requirement of the receiver is decreased, and the signal processing framework in the receiver is simplified.4. Aiming at the complex electromagnetic environment, the pace-time-frequency 3-D optimization problems of the airborne cognitive MIMO radar within the clutter and stable colored noise environment are discussed. The colored noise is suppressed by the waveform optimization, while the clutter is suppressed by the space-frequency optimization. Further more, when a clutter and unstable colored noise environment is considered, the effect of the clutter, jamming as well as the colored noise are reduced by the space-time-frequency joint optimization at the same time.