Towards Fully Integrated Low-Cost Inductive Powered CMOS Wireless Temperature Sensor

Abstract

We describe the complete monolithic integration of an inductive powered wireless sensor system using commercial complementary metal–oxide–semiconductor technology. The wireless system includes: two on-chip inductors used for communication and polarization, a cross-coupled oscillator for communication ( $\text{935.6 MHz}$ ), an inductive coupled energy receiver system ( $\text{13.5 MHz}$ ), a signal converter that converts constant current signals into pulses of modulated width, an asynchronous controller for autonomous operation of the chip, and an integrated temperature sensor. The chip was wirelessly biased by an inductive power transfer link at a distance of $\text{2 mm}$ . The signal transmitted by the chip was detected by a spectral analyzer and a dipole antenna up to a distance of $\text{110 cm}$ with an intensity of $\text{-88 dBm}$ . The integrated temperature sensor shows a linear response ( $R^{2} = 0.9968$ ) and presents a sensitivity of $\text{192, 94}\text{ Hz}/^{\circ }\text{C}$ . The full system occupies $74.93\%$ of an area of $\text{1.5 mm}$ $\times$ $\text{1.5 mm}$ . This wireless system is functional out-of-the-box without the need for additional components or post-processes. This integration leads to more robust, smaller, and a potentially cheaper wireless sensor systems, and provides new opportunities for size- and cost-sensitive applications.