Experiment of FMCW Radar for Small Displacement Detection using VNA

Small displacement detection is indispensable for the monitoring process in several fields such as the health of large building structures, landslides, monitoring of vibrations in large mechanical structures, and also in the health sector. Noncontact monitoring processes will provide an advantage in covering a large area operation. The radar system is potentially applied as a noncontact sensor. However, small displacement detection requires high resolution referring to the range resolution perspective. Detecting a small displacement on a millimeter to centimeter scale requires a very wide bandwidth. The main information to be obtained from small displacement detection is the distance of the target and the size of the small displacement. Frequency modulation continuous wave (FMCW) is a radar system that has been widely used in various fields. In this paper, a small displacement detection method is proposed by developing the detection capabilities of the FMCW radar. The ability to detect distance using beat frequency identification is maintained and phase detection is elaborated to detect small displacement without having to increase bandwidth. The experimental modeling of proposed FMCW using a vector network analyzer (VNA) was conducted in this study. The results show that the proposed FMCW system using VNA has the ability to detect small displacement with average phase shift of 0.41 radians for a 2 mm shift in the direction close to the target and 0.44 radians for the direction away from the target.