Low complexity portable MIMO radar system for the characterisation of complex environments at high resolution

This study presents the concept, design, and operation of a low-cost and lightweight multiple-input multiple-output (MIMO) radar system, dedicated to the characterisation of complex volumetric environments such as snow, forest, sand etc. using synthetic aperture radar tomographic focusing. The system consists of six transmitting and six receiving antennas, operated in a multi-static configuration, resulting in an equivalent mono-static vertical virtual array. Antenna positions have been set considering a trade-off between coupling effects, imaging ambiguities due to spectral folding and vertical resolution. The system also contains radio frequency signal generation and acquisition blocks and has been developed and operated at the IETR laboratory of the University of Rennes 1. An element-orthogonal frequency division multiplexing technique is proposed that avoids the use of switches for selecting transmission and reception channels, using a specific carrier for each transmit channel, and spectral analysis of each receive channel, allowing the 36 MIMO channels to be retrieved. The use of a time-domain back-projection algorithm for imaging in the elevation direction provides results that confirm the potential of the system for the characterisation of complex media.