**5. Evaluation of 17 GHz MIMO radar**

A prototype MIMO radar based on the above design was built and evaluated. We used a patch antenna for the array antenna element [12], which has a wide beam in the horizontal direction and sharp beam in the vertical direction, to avoid the ground surface clutter. We adopt FMCW radar system, and the antennas were connected with coaxial cables through a 16ch semiconductor switch.

Experiments were conducted to evaluate the MIMO radar system. **Figure 4** shows the MIMO radar facing the targets. A 15 cm trihedral square metal corner reflector is placed at 5 m from the center of the radar. In addition to the corner reflectors, there are also some targets. **Figure 5** shows the reconstructed SAR intensity image. In **Figure 5**, we can find the image of the corner reflector at ½ �¼ *X*, *Z* ½ � 0, 5 . The images of other targets are also formed accurately; we think the system works properly.

**Figure 4.** *The 17 GHz MIMO radar and targets.*

**Figure 5.** *The reconstructed SAR intensity image of the 17 GHz MIMO radar.*

**Figure 6.** *SAR interferograms when the displacement of all five patches is –4 mm. The positions of the displacement are also shown.*

We will use the prototype MIMO GB-SAR for ground surface displacement measurement. In order to evaluate the capability of DInSAR, we made a wooden wall having 10 m width and 2 m height, with 20 cm 20 patches, which will be displaced from the flat surface. This wall has five displacement patches at 2.5 m intervals. The wall has a rough surface to suppress the specular reflection. In this experiment, the distance from the radar to the wall was 10 m. **Figure 6** shows SAR interferograms when the displacement of all five patches is –4 mm. At this time, pixels below 35 dB were masked in the SAR intensity image in order to extract the displacement on the wall surface. Also, the squares in **Figure 6** indicate the position of each displacement plane.

We can confirm that the displacement was detected at the position of each displacement plane in **Figure 6**; **Figure 7** shows a comparison of displacement and

**Figure 7.** *A comparison of displacement and estimated displacement in each displacement plane.*
