Abstract
MIMO radars with electromagnetic vector sensor (EMVS) antennas (also
known as EMVS-MIMO radars) have been investigated intensively for target
direction estimation in recent years. Many existing works on this topic
are based on an unrealistic assumption that each EMVS antenna transmits
six identically polarized and mutually orthogonal waveforms.
Furthermore, target-fluctuation induced non-coherent backscattering in
polarization has been entirely overlooked. This paper aims to develop a
general transmit-receive signal model for EMVS-MIMO radar direction
estimation. Specifically, by taking transmit polarization agility and/or
polarization non-coherent backscattering into account, the collected
pulse signals are no longer of complete polarization, but of incomplete
polarization. By regarding an incomplete polarized (IP) signal as two
incoherent completely polarized (CP) signals with the same
azimuth-elevation directions and drawing upon the idea of ESPRIT, a new
azimuth-elevation direction estimation algorithm is thus derived. The
advantage of the new algorithm is that it can provide closed-form,
automatically paired azimuth-elevation direction estimates and require
no information on the location/displacement of the transmit-receive
antennas. Finally, simulations are conducted to demonstrate the
effectiveness of the proposed algorithm.