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Review
. 2018 May 28;18(6):1734.
doi: 10.3390/s18061734.

Reader Architectures for Wireless Surface Acoustic Wave Sensors

Fabian Lurz  1 , Thomas Ostertag  2 , Benedict Scheiner  3 , Robert Weigel  4 , Alexander Koelpin  5
Affiliations
Review

Reader Architectures for Wireless Surface Acoustic Wave Sensors

Fabian Lurz et al. Sensors (Basel). .

Abstract

Wireless surface acoustic wave (SAW) sensors have some unique features that make them promising for industrial metrology. Their decisive advantage lies in their purely passive operation and the wireless readout capability allowing the installation also at particularly inaccessible locations. Furthermore, they are small, low-cost and rugged components on highly stable substrate materials and thus particularly suited for harsh environments. Nevertheless, a sensor itself does not carry out any measurement but always requires a suitable excitation and interrogation circuit: a reader. A variety of different architectures have been presented and investigated up to now. This review paper gives a comprehensive survey of the present state of reader architectures such as time domain sampling (TDS), frequency domain sampling (FDS) and hybrid concepts for both SAW resonators and reflective SAW delay line sensors. Furthermore, critical performance parameters such as measurement accuracy, dynamic range, update rate, and hardware costs of the state of the art in science and industry are presented, compared and discussed.

Keywords: frequency measurement; pressure sensor; surface acoustic waves; temperature sensor; torque sensor; transceiver architecture; wireless sensor.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic layout of passive surface acoustic wave (SAW) devices for sensor applications.
Figure 2
Figure 2
Sensor and current reader architectures with their classification for wireless SAW instrumentation.
Figure 3
Figure 3
Block diagram of a monostatic reader concept for frequency domain sampling with frequency modulated continuous wave (FMCW) or frequency stepped continuous wave (FSCW) interrogation.
Figure 4
Figure 4
Signal processing flow chart for frequency domain sampling with reflective delay line SAW sensors.
Figure 5
Figure 5
Signal processing flow chart for frequency domain sampling with resonant SAW sensors. (a) direct calculation of the resonance frequency from the sampled frequency points; (b) calculation of the resonance frequency using additional software time-gating to mask static reflections of the environment as well as mismatches and crosstalk within the front end.
Figure 6
Figure 6
Block diagram of a monostatic reader concept using switched frequency stepped continuous wave interrogation for reflective delay line SAWs.
Figure 7
Figure 7
Schematic drawing of a reflective delay line SAW interrogation with a pulse radar based SAW reader.
Figure 8
Figure 8
Block diagram of the reader concept for time domain sampling with digital frequency estimation.
Figure 9
Figure 9
Block diagram of the reader concept for time domain sampling with digital frequency estimation.
Figure 10
Figure 10
Block diagram of the reader concept for time domain sampling with instantaneous frequency measurement.
Figure 11
Figure 11
Passive structure of a six-port interferometer formed by a Wilkinson power divider and three 90° hybrid couplers.
Figure 12
Figure 12
Block diagram of the reader concept for time domain sampling with pulsed frequency modulation (FM)/amplitude modulation (AM) tracking loops.
Figure 13
Figure 13
Pulsed FM/AM tracking loops with three-point interrogation strategy.
Figure 14
Figure 14
Pulsed FM/AM tracking loops with FM interrogation strategy and signed phase evaluation.
Figure 15
Figure 15
Pulsed FM/AM tracking loops with two-point interrogation strategy.
See this image and copyright information in PMC

References

    1. Dias J., Karrer H. Stress effects in acoustic surface-wave circuits and applications to pressure and force transducers; Proceedings of the 1974 IEEE International Solid-State Circuits Conference; Philadelphia, PA, USA. 13–15 February 1974; pp. 166–167. - DOI
    1. Reeder T.M., Cullen D.E., Gilden M. SAW Oscillator Pressure Sensors; Proceedings of the 1975 Ultrasonics Symposium; Los Angeles, CA, USA. 22–24 September 1975; pp. 264–268. - DOI
    1. Reeder T.M., Cullen D.E. Surface-acoustic-wave pressure and temperature sensors. Proc. IEEE. 1976;64:754–756. doi: 10.1109/PROC.1976.10205. - DOI
    1. Hauden D., Michel M., Gagnepain J.J. Higher Order Temperature Coefficients of Quartz SAW Oscillators; Proceedings of the 32nd Annual Symposium on Frequency Control; Atlantic City, NJ, USA. 31 May–2 June 1978; pp. 77–86. - DOI
    1. Wolff U., Dickert F.L., Fischerauer G.K., Greibl W., Ruppel C.C.W. SAW sensors for harsh environments. IEEE Sens. J. 2001;1:4–13. doi: 10.1109/JSEN.2001.923583. - DOI