Maximum accuracy evaluation scheme for wireless saw delay-line sensors

Abstract

This paper describes an evaluation scheme that prevents phase ambiguity of surface acoustic wave (SAW) delay-line sensors. Although it is well-known that phase evaluation yields accuracies of 150~1500 times higher than time-delay evaluation, the problem of phase ambiguity has prevented phase evaluation of sensors operating over a range larger than 2 pi. This paper addresses this unsolved problem with a complete strategy. Furthermore, the existence of an optimum choice of the relative reflector positions on the sensor is shown. The presented relations enable the design of maximum accuracy SAW delay-line sensors.

Surface acoustic wave devices for chemical sensing and microfluidics: a review and perspective

“…Here, there is a first IDT that generates the SAW, which propagates through the sensing area, and the modulated SAW is subsequently detected by a second IDT, generating an electrical signal on the IDT. 53 The distance between the input IDT and readout IDT is the delay line, and the sensing layer is deposited in this region of the substrate. 54 SAW delay line devices can be designed as one- or two-channel devices, where the latter consists of two SAW delay line devices fabricated parallel to each other.…”

Model-Based Identification Method for Pulse Position Coded Surface Acoustic Wave Identification Tags

“…Since the SAW tags were produced using a substrate with a low temperature coefficient of delay (TCD) [1], [20], [30], which affects the thermal expansion of the piezoelectric substrate and the temperature-dependent variation of the propagation velocity of the SAW, the differences in amplitude at high temperatures were minimal. Furthermore, the TCD of the second order is negligible here, and the assumption of a linearly scaled PPC grid due to temperature variations is justifiable.…”

“…D ELAY-LINE-based surface acoustic wave (SAW) sensors provide the capability of simultaneous tag identification and sensing of physical quantities such as, e.g., temperature, stress, or pressure [1]- [4]. They reliably work even in harsh environments and have been used in a wide variety of applications whenever standard sensors fail due to high temperature, radiation, or accelerations [5]- [7].…”

Surface Acoustic Wave RFID Tags

“…In this modulation scheme, the phase is used to determine the time position of the reflected pulse. It is evident that the uncertainty of measurement of phase of reflected responses depends on the signal-to-noise ratio (Kuypers et al, 2008). The needed strength of signal increases with increasing accuracy of phase values used for encoding.…”