A proximity wireless sensor based on backscatter communication

A proximity sensor is designed as an antenna-based sensor, operating at 2.4 GHz. The operating principle relies on the fact that when an object approaches an antenna, it affects its radiation properties and its input impedance. A diode power detector is used to sense the antenna input impedance variation as a reflected wave at the input terminals of the antenna. The detector output analog dc voltage is read using an analog-to-digital (ADC) of a low power microcontroller and subsequently it is conveyed back to a reader using UHF backscatter communication based on the WISP architecture.