Influence of coil design on sensing performance of pressure sensor with polyimide membrane

The objective of this research is to study various coil designs and to propose the pattern that can improve the performance of the pressure sensor. Wireless pressure sensor, based on polyimide foil, is designed, fabricated and tested. The proposed sensor is realised in heterogonous integration process and consists of PCB (Printed Circuit Board) coil, spacer and polyimide membrane with attached LTCC (Low Temperature Co-fired Ceramic) ferrite. Pressure variations are wirelessly detected in system antenna-sensor resonant frequency, by a phase-dip technique. The distance between the coil and the ferrite varies with an applied external pressure and consequently membrane deflection, so the inductance of the coil increases and the resonant frequency of the system decreases. The effect of coil designs with different number of turns is examined and sensor performances are compared. Experimental measurements are determined and confirmed by analytical calculations and simulated results.