A six-port interferometer based micrometer-accuracy displacement and vibration measurement radar

Displacement detection and vibration measurements are important requirements for automation and mechanical stress diagnosis in diverse industrial environments. Laser interferometry is a widely used technique for these kinds of measurements since it features high-resolution, wide dynamic range and wide frequency response. Another advantage of the laser interferometry technique is contactless diagnosis/sensing which allows remote operations. However this technique is not suitable in harsh environments for instance with the presence of dust or fog which occur in several industrial production sites. In this paper a new contactless radar based vibration measurement technique is presented. It features an RF frontend based on a passive six-port interferometer working at 24 GHz. A dedicated signal processing unit is also presented. The proposed hardware allows to measure with a position accuracy of 0.5 µm.