Clutter rank Of MIMO radar with a speical class of waveforms

In this paper, the rank of clutter covariance matrix (CCM) is studied for space-time adaptive processing (STAP) implemented on the multiple-input multiple-output (MIMO) radar with waveform diversity. It is found that the clutter rank is dependent on the rank and structure of the covariance matrix of the transmitting waveforms, and that clutter rank of orthogonal waveforms acts as the upper bound for all kinds of waveforms. More specifically, three simple rules are proposed to estimate the clutter rank for one special class of waveforms. This class of waveforms, though we call it special, indeed can include coherent waveforms, orthogonal waveforms, as well as part of partially correlated waveforms. In this way, the method of estimating the clutter rank for both coherent and orthogonal waveforms are herein unified. The application of these rules only requires the computation of the waveform covariance matrix (WCM) and a polynomial based on the WCM, thus it is convenient and computationally efficient. The proposed rules are well verified by simulation results and also general enough to be suitable for both conventional space time radar systems and the MIMO radars with orthogonal waveforms.