Dynamic range considerations in code division multiple input multiple output radar

Abstract

Multiple input multiple output (MIMO) beamforming is examined both theoretically and experimentally to highlight practical performance aspects that require a careful understanding when deciding if the MIMO concept is appropriate for a given application. Specifically, the time division multiplexing (TDM) and code division multiplexing (CDM) cases are compared. While both TDM and CDM form beams that agree closely with predictions, there are significant differences in system performance due to limits on the orthogonality of waveforms that occur when using CDM. These limits are manifested in the peak-to-mean sidelobe ratios, resulting in significant and extended range sidelobes consistent with a value approximately equal to the time-bandwidth product, and fairly independent from the number of transmitters or receivers used. In many cases, these sidelobes fundamentally limit the dynamic range of the radar. Simulations and experiments using a TDM/CDM MIMO radar validated these observations.