Standoff Non-Line-of-Sight Vibration Sensing Using Millimeter- Wave Radar

We explore the use of W-band frequency-modulated continuous wave (FMCW) millimeter-wave radar to detect the small micron-order vibrations induced when machining metallic objects. The advantage of using millimeter-wave frequencies is its ability to penetrate appropriate materials, leading to its application in sensing vibration behind objects in non-line-of-sight (NLOS) environments. We demonstrate the ability to reliably detect vibration on the order of 10 microns of reflective objects through a lossy inhomogeneous material. From these results, FMCW millimeter-wave radar shows promise to be incorporated as an inexpensive sensor in systems that require knowledge of vibration profiles in NLOS environments.