The input of RangeDopplerResponse is a matrix reprsents fast time and pulses. Therefore, if you have a TDM MIMO radar, you can either use the received signal at a give element or do beamforming across the virtual array to obtain such an input. Once you get that matrix, the NTx and NRx no longer affect your result. They only play a role when you do beamforming
The fast time of a MIMO radar is the same as a regular radar, so nothing special on that dimension. For velocity, you need to provide the correct PRF. Because you do TDM, you need multiple pulses to construct one virtual array. Therefore you must take that into consideration and provide correct PRF information.
HTH
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