Implementation of Multiparameter Monitoring by an <italic>LC</italic>-Type Passive Wireless Sensor Through Specific Winding Stacked Inductors

Abstract

A traditional LC-type passive wireless sensor has been used for the measurement in sealed environments. Due to the limitation of its operation principle, this method was only suitable for a single parameter monitoring. For most applications, it is desirable for multi-parameters to be monitored. In order to keep the chip area of the sensor as small as possible, multi-level inductors may be coaxially stacked. However, the transmitting signals affect each other due to strong mutual coupling between the stacked inductors. This paper presents a novel inductor structure by using a specific winding to achieve the minimized mutual inductance. Using the partial inductance theory, the mutual inductance of two stacked inductors is analyzed. Simulations of the two stacked inductors coaxially aligned, with each connected in a variable capacitor, show that the mutual inductance between the two inductors can be greatly suppressed. This phenomenon has also been verified through multi-layer PCB inductors. And capacitive temperature and pressure sensors were linked to the two stacked inductor to implement the simultaneous measurements of temperature and pressure. The measurement results indicate that the sensitivity of the temperature sensor is about 41.67 kHz/°C between -20°C to 100°C while the sensitivity of the pressure sensor is about -133.33 kHz/kPa between 50kPa to 110 kPa.