Untersuchungen zur Modellierung und Optimierung von Oberflächenwellen-Bauelementen und Auswerteschaltungen für die Gassensorik

This work describes the application of polymer coated surface acoustic wave (SAW) devices as gas sensors. It focuses on the characterization and modelling of SAW resonators. Additionally SAW delay lines and thickness shear mode devices are described. The major effects of the sorption of gas molecules into the polymer coating are the increase in mass and changes in the viscoelastic and electric behaviour of the coating. Modells are explained that allow to calculate the influence of these effects on the velocity and damping of a surface acoustic wave. The SAW sensors are characterized by measurement of the scattering parameters with a network-analyzer. Furthermore an oscillator with adjustable phase is presented that allows to measure not only the resonance frequency but also the damping of a sensor. The influence of temperature, humidity and changes in the concentration of toluene are examined. The results of the scattering parameter measurements show that the phase at which a sensor is operated in an oscillator has a strong influence on the sensitivity. By choice of the phase it is possible to distinguish changes in humidity from changes in the toluene concentration. This can also be seen from measurements with an oscillator where the phase has been modulated. In a second theoretical part a model based on the Coupling of Modes (COM) approach is presented. This model allows to calculate the transmission behaviour of a SAW sensor in form of scattering parameters when the properties of the piezoelectric substrate and the geometrie of the electrodes are known. This model is extended to cover the influence of a coating. Thereby the transmission behaviour of a sensor can be calculated from the parameters of substrate, geometrie and thickness, density as well as viscoelastic behaviour of the coating. This model is used to examamine possibilities for the optimization of SAW gas-sensors and the design of oscillators for these sensors.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2002

Author dc:creator

• Oechtering, Peter

Contributors dc:contributor

• Mokwa, Wilfried

• info:eu-repo/classification/ddc/530
• Physik
• Gassensor
• Oberflächenwelle
• Oszillator
• Coupling-of-Modes
• SAW

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-120656%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:58824