Derivative constrained Capon estimator using integrated mode vector

The derivative constrained Capon estimator using an integrated mode vector (DECCIM) suitable for automotive radar is proposed. The DECCIM estimates angular spread (AS) and direction-of-arrival (DOA) of a reflection signal composed of several element waves reflected simultaneously from an object. It uses an integrated mode vector in which AS is considered. In addition, its constraint condition includes the derivative of the integrated mode vector. The estimation performance is demonstrated via some numerical examples. When all of phases of the element waves are 0 degree and SNR is greater than 60 dB, the estimation errors of AS and DOA are less than 0.8 degrees and 0.1 degrees, respectively. The standard deviations of AS and DOA are less than 0.5 degrees. On the other hand, the standard deviation of AS is 2.1 degrees when the phases of the element waves are given at random. In order to improve the estimation accuracy of the DECCIM, we also propose the DECCIM using the forward/backward spatial smoothing processing.