LAUSR

A recent method proposed by L. L. Guo, H. Deng, and B. Himed in “Waveform Optimization for Transmit Beamforming with MIMO Radar Antenna Arrays,” IEEE Trans. Antennas Propag. vol. 63, no. 2, pp. 543–552, Feb. 2015, claims that the multiple-input multiple-output (MIMO) radar can form a transmit beam pattern with nulls in specific directions to alleviate the clutter and make the radar signals undetectable with initial phase optimization. However, it lacks some of the important aspects and may create an incorrect impression about transmit beamforming of MIMO radars. This comment shows that the virtual transmit beam pattern cannot reflect the practical radiation energy of the radar array. Even the virtual transmit beam pattern has nulls in the preselected directions, the clutter from these directions cannot be alleviated at the radar receiver, and the MIMO radar signals would still be detectable in these directions.