Human Presence Detection Sensor Using Polarization Insensitive Metamaterial Absorbers

Non-invasive crowd estimation has remained a challenging issue among researchers. Methods such as image analysis and Wi-Fi/Bluetooth probing can always be used to identify and track people. Lately, the authors have introduce a non-invasive method for crowd estimation based on ambient RF energy measurements. In this paper, a sensitive sensor based on metamaterials is introduced to measure the variations within an environment of the available RF energy levels for crowd estimation purposes. Considering human body resonance at 2 GHz, a metamaterial absorber is designed to operate at 2.4 GHz while remaining insensitive to polarisation and incident angle. This absorber, is equipped with a feed network and rectifier to efficiently absorb and transfer the maximum available Wi-Fi energy into a measurable DC voltage. To evaluate the performance of the sensor, the proposed structure is fabricated as an array, and its performance is tested in both the lab and a controlled real-world environment.