| Since the concept of Multiple-input multiple-out (MIMO) radar is proposed, it hasattracted great concerns from the radar researchers. The MIMO radar theory is rapidlydeveloped. The existing studies have shown that the MIMO radar has obviousadvantages compared to phased array radar in terms of target detection, parameterestimation, etc.. In the dissertation, the application of MIMO radar in airborne radar isstudied, the main contributions are:(1) MIMO radar array configuration and equivalent transmit-receive beamformingMIMO radar array configuration has more flexibility compared to phased radar. Adetailed analysis of the various array configuration of MIMO radar is made in thedissertation, and the characteristic of each array configuration is discussed. Based on thesimulated annealing, a sparse array designing of MIMO radar is proposed. Due to theimportance of subarray MIMO radar, the equivalent transmit-receive beamforming isgiven. How to make a fair comparison of MIMO radar and phased array radar is animportant topic, it is also the basis of evaluating whether MIMO radar has superiority.The relationship of output signal to noise ratio (SNR) between MIMO radar and phasedarray radar is derived, the fair comparison conditions should be set as follows: theMIMO radar and phased array radar should have the same number of antennas, and thenumber of pulses transmitted in one coherent processing interval (CPI) of MIMO radarshould be equal to the product of the number of pulses transmitted by phased array radarand the number of orthogonal signals transmitted by MIMO radar.(2) Estimation of clutter rank of MIMO radar in case of subarrayingThe MIMO radar signal model is introduced. The concept and importance ofclutter rank are discussed. Due to the subarray MIMO radar has the advantages ofphased radar and MIMO radar, and it can reduce the system complexity of generatingorthogonal signals and signal processing. Thus, the subarray MIMO radar is more likelyto be used in practical applications. The estimation method of clutter rank of MIMOradar in case of subarraying is proposed, which can provide theoretical basis for thesubarray MIMO radar space-time adaptive processing (STAP) designing. Since the existing clutter rank estimation methods are not suitable to the MIMO radar which ishighly sparse, the clutter rank estimation method of MIMO sparse radar is introduced.(3) Airborne MIMO radar reduced-rank STAP algorithmsThe fundamental principle of airborne radar STAP is introduced, and thereduced-rank STAP algorithms in MIMO radar are discussed. The principles ofapplication of principal component (PC), cross spectral metric (CSM) and multi-stagewiener filter (MSWF) reduced rank STAP algorithms in MIMO radar are given. TheSTAP performances are compared for different reduced rank STAP algorithms.(4) Airborne MIMO radar reduced-dimension STAP algorithmsThe equivalence of space-time domain STAP and transform domain STAP isdeduced, several typical reduced-dimension STAP algorithms are introduced. Becausethe flexible array configuration and equivalent beamforming ability, the traditionalSTAP algorithms of phased array radar are difficult to be used in MIMO radar directly.Based on the joint domain localized (JDL) algorithm, the proposed auxiliary beamselection method for MIMO radar reduced-dimention STAP which can be used fordense array, partially sparse array and sparse array. The subarray MIMO radar can beviewed as a special case of MIMO partially sparse radar. Thus, this method also can beextended to subarray MIMO radar. The auxiliary beam selection method for subarrayMIMO radar is discussed.(5) A method for finding best channels in beam-space post-Dopplerreduced-dimension STAPMotivated by the cross-spectral metric which evaluates the significance ofeigenvectors, a method for finding best channels as the auxiliary channels to cancel theinterference components in reduced-dimension STAP is proposed. The proposedalgorithm can achieve the best output SINR performance by selecting the best channelsas auxiliary channels when the degrees of freedom of a STAP system are fixed.Generally,3~5channels are enough even when the clutter covariance matrix isunknown. The superiority of this algorithm is acquired at the cost extra computationburden, a possible operating mode is proposed. |
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