An RF backscatterer system for real-time multi-sensing applications

Abstract

In this paper, a power-efficient passive analog frequency modulation based RF system is proposed for real-time communication with multiple sensor elements for internet-of-things (IoT) based smart applications. The proposed RF tag with integrated sensors uses an onboard ultra low power oscillator to generate a single frequency modulation signal unique to each of the sensor elements. The generated single tone frequency is modulated to generate the backscattered RF signal, which is immune to the interference present in the propagating environment. The maximum power required for continuous operation of the sensing oscillator is 30 μW, which is harvested from the received RF signal. The designed multi-sensor RF tag has a sensitivity of −6 dBm and has the capacity to integrate up to six different sensors within the available single channel RFID bandwidth of 300 kHz. The wireless communication distance of 10 ft is achieved due to the low power consumption of the multi-sensor RF tag. A passive RF tag with two example sensing elements; temperature and luminescence are demonstrated. The temperature and luminescence change from 25 °C to 60 °C and from 0 to 20 footcandle (lumen/ft2) is represented by 75–100 kHz and 125–150 kHz frequency range, respectively.