MIMO-OFDM Radar Systems for Ambiguity Control With Hybrid Range- and Doppler-Division Multiplexing

Conventional multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) radar systems typically adopt the equidistant subcarrier interleaving (ESI) scheme to generate orthogonal transmit (TX) waveforms in the frequency domain. However, the ESI scheme is limited by a reduced unambiguous distance and distance-dependent angle errors. To mitigate these issues, this paper proposes a hybrid range- and Doppler-division multiplexing (RDM-DDM) scheme for MIMO-OFDM radar, which separates TX signals in both the distance and velocity domains. We first establish the signal model for the hybrid MIMO-OFDM radar system. At the receiver, we implement distance–velocity–angle processing using fast Fourier transforms (FFTs). Additionally, an ambiguous-cell Doppler correction algorithm is applied to mitigate intercarrier interference (ICI) and resolve velocity ambiguity. This hybrid scheme increases the number of virtual MIMO channels, eliminates distance-dependent angle errors, and enhances angle estimation accuracy. Furthermore, it overcomes the inherent limitations of standalone RDM or DDM, allowing for adaptive control of unambi guous distance and velocity by adjusting the hybrid ratio. Simulations based on a 77-GHz 8 × 8 antenna array configuration validate the effectiveness and superior performance of the proposed schemes.