Chipless RFID Sensor Detecting the Angle and Width of Crack in the Metal With High Sensitivity

In this article, a metal crack sensor based on chipless radio frequency identification (RFID) technology is proposed. It is used to monitor the angle and width of cracks in the Internet of Things (IoT). The sensor is composed of square, rectangular, and bow-tie patches and operate within the frequency range of 3.5–7 GHz. By using polarization multiplexing and a modified bow-tie patch, the sensitivity of the sensor is improved. The results show that the sensor can accurately identify the cracks along the directions of 0°, 45°, 90°, and 135°. The corresponding sensitivity in each direction is 50.20 MHz/0.1 mm, 23.50 MHz/0.1 mm, 50.41 MHz/0.1 mm, and 33.88 MHz/0.1 mm. The sensor has the characteristics of passive, low-cost, and simple structure.