Reinhard Steindl

Impedance loaded SAW-sensors offer a wide range of measurement opportunities

SAW ID-tags can be employed as passive transponders for conventional sensors of capacitive, inductive and resistive type. An interdigital transducer (IDT) is used as a loadable reflector, other fixed reflectors are used as reference bits. The load of the programmable reflector influences both the phase and amplitude of the reflected wave. The principle is discussed, applications for the measurement of light, pressure and temperature are presented.

SAW delay lines for wirelessly requestable conventional sensors

Programmable reflectors of SAW ID-tags can be employed as passive transponders for conventional sensors of the capacitive, inductive and resistive type. The programmable reflector is a loadable split finger transducer, other fixed reflectors are used as reference bits. A noncoherent read out signal processing is sufficient, because the load of the programmable reflector influences both the phase and amplitude of the reflected wave. The principle is discussed, setup and results of some actual measurements are presented.

Wirelessly interrogable magnetic field sensor utilizing giant magneto-impedance effect and surface acoustic wave devices

A micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30 /spl mu/m diameter amorphous FeCoSiBNd wire of zero magnetostriction. Surface Acoustic Wave (SAW) devices are described as passive, radio requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors. In order to develop a wirelessly interrogable magnetic field sensor, the combination of GMI sensors and SAW transponders is discussed by several measurements. The device shows a relative signal sensitivity of 80 dB/T at low magnetic flux density B<30 mT, quick response (/spl ges/40 MHz bandwidth), and a high-temperature stability.

Impedance loaded SAW sensors offer a wide range of measurement opportunities

Surface-acoustic-wave interdigital tags can be employed as passive transponders for conventional sensors of capacitive, inductive, and resistive types. An interdigital transducer is used as a loadable reflector, while other fixed reflectors are used as reference bits. The load of the programmable reflector influences both the phase and amplitude of the reflected wave. The principle is discussed, and applications for the measurement of light, pressure, and temperature are presented in this paper.

Cordless batteryless wheel mouse application utilizing radio requestable SAW devices in combination with the giant magneto-impedance effect

Surface acoustic wave devices for wireless identification (ID) systems, the so-called ID tags, can be turned into novel sensor elements (transponders) for impedance sensors by making use of magnetic-field variations caused by the wheel rotation and key-click functionality of a personal computer (PC) mouse. This kind of sensor does not need any power supply and may be interrogated wirelessly. Interdigital transducers are used as loadable reflectors, while another fixed reflector is used as reference to compensate cross sensitivity for temperature, mechanical stress, etc. The load of the reflectors influences amplitude and phase of the reflected wave. The loads impedance is changed utilizing the giant magneto-impedance (GMI) effect in a 30-/spl mu/m-diameter amorphous FeCoSiNd wire of zero magnetostriction. The measurand, represented by the PC-mouse key clicks and wheel rotation, influences a magnetic field, which varies the impedance of the GMI wire. Consequently, the load of the reflector influences the reflected acoustic wave and the response signal of the radio sensor. The operating principle of such a magnetic-field sensor is discussed, and the tuning for an application in a passive and cordless PC mouse is presented.

Wirelessly interrogable sensors for different purposes in industrial radio channels

The radio request of passive wirelessly interrogable surface acoustic wave sensors is discussed. The parameters of the measurement process are divided to the contributions of the sensor, the radio channel and the radio request method. The measurement bandwidth and an example for an actual radio channel are discussed. For matching of the method to the measurement problem, the parameters of different radio request methods are estimated.

State of the art radio interrogation system for passive surface acoustic wave sensors

The radio request of passive wireless interrogable surface acoustic wave (SAW) sensors/transponders, is discussed and a radio interrogation system for passive SAW sensors is introduced. The concept is intended to provide an alternative to interrogators with expensive RF and signal processing effects. Consequently the presented system employs a new concept for the generation of the RF signals and for signal windowing. Considering the inherent limitations, the proposed system presents a simple low cost solution for a wide range of various applications. Additionally we have investigated a new, small size and light weight antenna design used in conjunction with the SAW devices to build the passive sensor/transponder. The antenna structure is based on the concept of folded spiral antennas. Details of this proposed multilayered planar antenna design are described and experimental results are discussed. Numerical simulation results compared with experiments are presented. The system shows satisfactory performance and applicability in a wide range of remote monitoring applications.

A new generation of passive radio requestable SAW sensors for ultra fast measurements

In this paper we discuss surface acoustic wave sensors for the measurement of dynamic measurands. The sensor types and the principles of effecting by the measurand are described. For non-stationary measurands, terms like bandwidth, resolution and error limits are discussed, boundaries are given. A new method of SAW radio sensors is introduced, capable for high speed measurements. Dynamic parameters are estimated experimental results are given for these new SAW sensor devices.