Target Localization in MIMO OFDM Radars Adopting Adaptive Power Allocation among Selected Sub-Carriers

Abstract

Multiple-input multiple-output (MIMO) radar has been introduced to enhance the performance of classical radar systems. Nevertheless, radar cross sections (RCS) fluctuations remains a known problem in radars. Target localization using narrowband signal produces reduced accuracy due to RCS fluctuations. One of the solution to this problem is utilization of frequency diversity of wideband signal. This paper presents target localization in MIMO radars using an adaptive orthogonal frequency division multiplexing (OFDM) waveform for effective frequency diversity utilization. Each transmitting antenna transmits an OFDM signal in different time slots and received by the each receiving antenna in the receiver array. A joint direction-of-departure (DOD) and direction-of-arrival (DOA) estimation scheme is applied to each of the OFDM sub-carrier using two-way multiple signal classification (MUSIC) algorithm. The estimation results at each sub-carrier are combined based on majority decision using angle histogram (non-parametric approach) to formulate the final wideband angle estimation. In addition, an adaptive power allocation among the sub-carriers is implemented, where the system evaluates the signal quality at each sub-carrier and consequently formulates a feedback to the MIMO transmitting side. The following transmission will comprise of OFDM waveform that focuses the transmit power at selected sub-carriers only. The sub-carrier selection is based on singular values obtained from singular value decomposition operation at each of the sub-carrier. The performance of the proposed scheme is evaluated through numerical simulations as well as validation by experiments in a radio anechoic chamber. It was demonstrated that the usage of larger number of sub-carriers improves the angle estimation accuracy.