Passive wireless UV SAW sensor

This paper presents studies of a passive wireless ultraviolet (UV) surface acoustic wave (SAW) sensor operating in the frequency range 436-440 MHz. The sensor contains two SAW delay lines (DLs). The first DL is measuring, and the second is the reference. In the measuring DL, receiving-transmitting inter-digital transducer (IDT) is connected to the antenna and the sensing element zinc oxide film. In the reference DL, the receiving-transmitting IDT is connected to another antenna and does not contain a UV-sensitive element. Two methods of information reading from the sensor are proposed: based on the Fourier transform of the frequency dependence of the parameter S11 of the reader antenna and using reading pulses of 1.5-mu s duration, which have carrier frequencies corresponding to the central frequencies of the measuring and reference channels. The sensor can measure UV intensities from 10 to 40,000 mu W/cm(2) with a maximum sensitivity of 6000 ppm/(mu W/cm(2)) at low intensities, and which rapidly decreases as the UV intensity increases (less than 100 ppm at the UV intensity of 40,0000 mu w/cm(2)).