An RF-powered temperature sensor designed for biomedical applications

An RF-powered temperature sensor with power management and communication circuits designed with a standard 130 nm CMOS technology is reported. The system was designed to have an RFID-like functionality, i.e., the device communicates with an external reader, receiving power and backscattering information. Initially, the system collects energy in a low-power charging mode, with a rectifier optimally designed to operate with signal levels as low as -10 dBm centered approximately 900 MHz. Operating at condition of minimum input power, the system takes around 70 μs to power up. A calibration method was designed to enable a measurement error of less than 0.1°C while the sensor operates in the human body temperature range (35 to 42 °C). The circuits were simulated in the Cadence Spectre environment and the total power consumption observed was approximately 8.5μW when in active mode and 4.9μW when in standby mode. Some parts of the circuit were measured and preliminary results are reported.