Due to a high demand for global Synthetic Aperture Radar (SAR) data sets, recent spaceborne sensors reach their limits in terms of resolution, swath width and repeat cycle. In addition, fully polarimetric operation reduces the maximum swath width approximately by the factor of two. To solve SAR inherent limitations, a new generation of sensors with multiple transmit and multiple receive channels (MIMO) and digital beam-forming (DBF) capabilities is suggested. Using a quad-polarized MIMO-SAR, transmitting simultaneously orthogonal waveforms in horizontal and vertical polarizations, enables data acquisitions without any reduction of the swath width or resolution. In this paper a concept is described, which uses an advanced filtering and processing method to separate the transmitted signals in the receiver and to measure all four parameters of the scattering matrix simultaneously. Ground-based MIMO-SAR measurement results are presented, which serve as a first verification of the suggested technique with an extended, non point-like target.