Design and fabrication of passive wireless sensor array system using composite coding resonant SAW transducer

Abstract

This paper presents a novel composite SAW (surface acoustic wave) passive wireless sensor system involving a resonator and a delay line. While the interrogational signal is a sinusoidal burst, the response is a delayed and damped oscillation. The frequency and the delay time of response are related to the measurand and the coding of the sensor element, respectively. The composite sensor consists of a SAW resonator and a delay line. It combines the advantages of these two devices and can be used as elements of multiple sensors for longer distance passive wireless measurements. As the wireless sensing response is weak and transient, in order to get the response with the maximum signal-to-noise ratio, the interrogational frequency is designed to be adjustable according to the result of frequency estimation. As a result, an optimal sensing result is achieved. In the transceiver set-up, the software DDS (direct digital synthesis) source with a rather high resolution is implemented to track the passive wireless sensor. An isolated switch is set in transmitter to depress the correlation leakage noise after switching off the wireless RF (radio frequency) interrogation signal. In this paper, the characteristics of the response, the working procedure of the signal processing, sensor temperature test results and the system error analyses are elaborated. A prototype instrument is built. Experimental results show the effectiveness of the instrumentation and the advantages of the composite sensor system.

A SAW passive wireless sensor system for monitoring temperature of an electric cord connector at long distance

“…The variation of natual frequency with the temperature can also be described as following equations: [2] (2)…”

“…However, with the increase of the distance, the receiving signal energy will be rapidly attenuated. The sensing distance of the conventional passive wireless sensor system is rather short (<10 m) due to low detecting sensitivity for the weak transient echo signal in the strong noise applications [1][2][3][4]. Up to now, the maximum detecting distance of the passive wireless sensor is 10 m [1][2][3][4].…”

“…The sensing distance of the conventional passive wireless sensor system is rather short (<10 m) due to low detecting sensitivity for the weak transient echo signal in the strong noise applications [1][2][3][4]. Up to now, the maximum detecting distance of the passive wireless sensor is 10 m [1][2][3][4]. Energy harvesting can provide a strong power for a longer distance (more than 100m) [5][6][7].…”

Detection using intermittent observations for passive wireless sensors

“…In the environmental monitoring domain, passive wireless sensors that detect bio-hazardous materials are explained in [18]. An example of a passive wireless sensor for measuring temperature, stress, strain, acceleration and displacement using Surface Acoustic Wave (SAW) transducer is described in [8]. In the health care domain, a passive strain-sensor technology for the measurement of small strains on bones or fixation systems in the human body is presented in [16].…”

Optimal performance for detection systems in wireless passive sensor networks

“…In the environmental monitoring domain, passive wireless sensors that detect bio-hazardous materials are proposed in [7]. An example of a passive wireless sensor for measuring temperature, stress, strain, acceleration and displacement using Surface Acoustic Wave (SAW) transducer is described in [8]. In the health care domain, a passive strainsensor technology for the measurement of small strains on bones or fixation systems in the human body is presented in [9].…”