A Low Noise CMOS Readout Based on a Polymer-Coated SAW Array for Miniature Electronic Nose

Abstract

An electronic nose (E-Nose) is one of the applications for surface acoustic wave (SAW) sensors. In this paper, we present a low-noise complementary metal–oxide–semiconductor (CMOS) readout application-specific integrated circuit (ASIC) based on an SAW sensor array for achieving a miniature E-Nose. The center frequency of the SAW sensors was measured to be approximately 114 MHz. Because of interference between the sensors, we designed a low-noise CMOS frequency readout circuit to enable the SAW sensor to obtain frequency variation. The proposed circuit was fabricated in Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 μm 1P6M CMOS process technology. The total chip size was nearly 1203 × 1203 μm2. The chip was operated at a supply voltage of 1 V for a digital circuit and 1.8 V for an analog circuit. The least measurable difference between frequencies was 4 Hz. The detection limit of the system, when estimated using methanol and ethanol, was 0.1 ppm. Their linearity was in the range of 0.1 to 26,000 ppm. The power consumption levels of the analog and digital circuits were 1.742 mW and 761 μW, respectively.

Bulk and Surface Acoustic Wave Sensor Arrays for Multi-Analyte Detection: A Review

“…Configurations include the combination of single-sensor devices in one measurement cell, the combination of measurement cells containing single sensors, and the combination of disposable sensor chips, i.e., single sensor devices with polymer housings [77]. When working with large-volume gas samples, several single-sensor devices can be exposed to the gases in a comparatively large measurement chamber as has been realized for QCM, FBAR, and SAW sensors [21,78,79]. With reduced sample volumes and particularly with liquid samples, however, the volumes required for uniform sampling of the sensors would be too high in the chamber setup.…”

“…A further development allowed the wireless readout of this setup, e.g., for wireless sensor network applications [47,167]. A low noise CMOS readout circuit was developed for an array consisting of five SAW LiNbO 3 resonators for differentiation between two aliphatic alcohols [79].…”