  State-of-the-art automotive radar sensors use a Mutliple-Input Mutiple-Output
(MIMO) approach to obtain a better angular resolution. Time-Division
Multiplexing (TDM) scheme is commonly applied to realize the orthogonality in
time at the transmitter. Apart from its simplicity in implementation, TDM
scheme has the drawback of a reduced maximum unambiguous Doppler proportional
to the number of transmitters. In this paper, a phase difference based Doppler
disambiguation method is proposed to regain the maximum unambiguous Doppler
which is equivalent to only one transmitter. This method works well when the
number of transmitters is large. The proposed method is demonstrated with
simulation and measurement data.
