An efficient waveform diversity based on variational mode decomposition of coded beat-frequency shifted signals algorithm for multiple-input multiple-output millimetre-wave imaging

Waveforms used in multiple-input multiple-output (MIMO) systems must be considered in such a way that individual transceiver (T-R) pairs can be separated from the composite received signal. An algorithm called variational mode decomposition of coded beat-frequency shifted signals (VMD-CBFSS) is presented for waveform diversity. First, transmitters are divided into several groups. A small shift is applied to the carrier frequency of the transmitters of different groups. Also, signals within each group are encoded by assigning a binary phase in a time block. On the receiver side, by using a multiresolution analysis technique, the combined signal is decomposed into its main frequency components and then the composite signals of each group are decoded to retrieve each T-R pair. VMD-CBFSS provides an efficient solution in terms of overall transmitting time and sampling rate in addition to robustness against channel noise. Moreover, the algorithm is employed in a near-field MIMO millimetre-wave imaging system, and results are presented in the form of numerical simulations.