Ultralow Read Sensitivity RFID sensor based on Tunnel Diode Voltage-Controlled Oscillator

Wireless, Batteryless technology holds unmatched potential for improving the efficiency of our societies, from identification & localization to sensing. The communications are typically asymmetric and involving a zero-energy transponder being activated by a remote Reader. Unfortunately, the communication distance is restrained by the minimum activation power (also named Read sensitivity) to commonly a dozen of meters. In this work, we combine a multistage charge pump rectenna with a ultra-low Voltage Controlled Oscillator (VCO), yielding to an unmatched power activation of -28.6 dBm (1.4 mu W). Under this condition, the rectifier yields in the order of 100 mV into a 100 mu F capacitor, which is enough to drive the VCO directly (no DC-DC involved) upon activation by a tilt switch sensor.