Doppler ambiguity resolving in TDMA automotive MIMO radar via digital multiple PRF

Multiple input multiple output (MIMO) radars require orthogonality between the transmitted signals, which can be achieved via time division multiple access (TDMA) scheme, where only a single transmitter operates at a predefined time slot. This scheme determines the pulse repetition frequency (PRF) per transmitter, which in turn limits the maximal unambiguous Doppler. When radars are designed to operate in an ambiguous Doppler regime, Doppler ambiguity is conventionally resolved via waveform diversity (e.g. multiple PRFs), which is practically challenging. This work proposes a method to resolve Doppler ambiguity by generating an additional PRF digitally, without waveform diversity. In the case where the transmitters are positioned linearly, the proposed method performs better for targets that lie in a limited field of view, compared to the array. The proposed method performance is evaluated via simulations, compared to the traditional processing method and tested using measurements, collected with an automotive radar in real-life scenarios.