**1. Introduction**

Ground based synthetic aperture radar (GB-SAR) has been used for the observation of the displacement of ground surface and can be applied, for example, to remote landslide monitoring. GPR is a useful method for shallow subsurface imaging and widely used for the detection of buried pipes. Conventional GB-SAR systems and GPR systems are equipped with a pair of a transmitting antenna and receiving antenna, and synthetic aperture radar (SAR) processing is applied to the data sets acquired by moving the pair of antennas.

Instead of moving antennas for radar imaging, we introduce MIMO technique, where we use fixed multiple antennas for equivalent SAR imaging. In both GB-SAR and GPR systems, we use multiple transmitting and receiving antennas equivalent to multiple-input and multiple-output (MIMO). This radar configuration is referred as multi-static radar. However, we acquire all the combination of transmitting and receiving antennas, which is not common in the conventional multi-static radar. This is the reason why we call it MIMO radar, and we show that it expands the potential of radar drastically. The targets of MIMO GB-SAR and MIMO GPR such as land slope and buried pipes are stational, and we can acquire radar signal from these targets by switching all the transmitting and receiving antenna combinations. We do not need orthogonal signal transmission for the identification of the transmitted signal by receiver, because signals can be separated by the time sequence.
