A Novel Microwave Architecture for Passive Sensing Applications

The use of radio-frequency signals for passive indoor applications has gained significant interest over the last years. By leveraging ubiquitous Wi-Fi signals, the Doppler information of a target can be retrieved after the analysis of measurements associated with the received signal strength (RSS), the channel state information (CSI), or with passive Wi-Fi radar (PWR) techniques. However, RSS and CSI-based strategies require digital signal processing of high computational cost and/or special modifications to the Wi-Fi access point, while PWR-based approaches rely on a reference channel and interference removal algorithms to provide Doppler information. In this work, a novel microwave architecture for passive sensing applications is proposed. By taking advantage of the reflected RF signals and the direct signals from a non-cooperative transmitter, the proposed architecture can provide the Doppler information of a moving target. Experimental results confirm the effectiveness of the proposed scheme for the remote detection of small amplitude motion.