Multi-Modal Radar Systems (MMRS) using Digital Beam-Forming (DBF) concept offer higher operational flexibility and improved performance compared to the conventional radar systems using analog beam steering. In particular, Synthetic Aperture Radar (SAR) based on DBF concept overcomes the fundamental limitation of classical SAR systems delivering high resolution and simultaneously wide swath images. This paper presents a laboratory prototype of the next generation MMRS system - a reconfigurable Multiple Input Multiple Output (MIMO) radar demonstrator based on the DBF architecture. The hardware configuration of the demonstrator is described in detail, and the system calibration and signal processing procedures are considered. The first measurement results confirming its functional capabilities are presented and discussed.