An interface chip for saw based sensor in an ad-hoc network

The design of a smart integrated chemical sensor system that will enhance sensor performance and compatibility to ad hoc network architecture remains a challenge. This work involves the design of an interface chip for a Surface Acoustic Wave (SAW) based chemical sensor where the sensor reflects the RF input and introduces a time delay proportional to the concentration of the vapors absorbed by it. The interface chip detects the frequency shift as a function of the chemical species absorbed by the sensor and alerts the ad hoc network controller when a monitored parameter exceeded some threshold, based on local processing and measurements. System components are designed in an RF environment to carry out the local processing and estimation of the chemical absorbed. Simulation results for individual circuit components as well as the complete chip outline the robust performance of the system that improves chemical target detection and reduce false alarms. The design takes into account a sensor system with ten chemical SAW sensors operating at a resonant frequency of 1 GHz and an attenuation of 30 dB. The circuit is designed in to produce an alarm signal for a frequency shift of 1kHz due to a change in chemical concentration at the sensor, in 0.35 µ technology. The performance of the chip can be improved by scaling the design to 0.18 µ technology