Information Technology Reference
In-Depth Information
4.3 E-eye with SAW retransmitter for wireless sensory networks
The hardware and software complex on a chip of the type “electronic eye” developed by us
can be technically improved using retransmitters on surface acoustic waves (SAWs) with the
RFID technology of real-time monitoring for the individual human biosafety (Fig. 32a,b) [1].
Fig. 32. (a) Wireless active (passive) SAW sensory micro-nanosystem with the LED
technology e-eye. (b) Intelligent wristwatch with the RFID technology and LED e-eye.
(c) Smartphone with the RFID technology for data processing from the wristwatch
The wireless SAW micro-nanosensory system consists of an antenna, interdigital
transducers (IDTs) and a set of reflecting electrodes located on a piezoelectric crystal. If the
antenna of the SAW sensor picks up a radio-frequency electromagnetic wave, then a
received electromagnetic signal is transmitted to IDTs which are in the form of plane
parallel electrodes on a substrate surface and are connected with each other through
common buses and after that to a special control unit starting the optical information read-
out. An outcoming time-lagged signal of spectral reflection characteristics enhances an
alternating electromagnetic field which has the significant impact on an anisotropic
dielectric and harmonic mechanical oscillations, tensions, strains caused by the inverse
piezoelectric effect and emerged in the SAW sensor substrate. Electric charges with unlike
signs are produced on the crystal surface which conditions the onset of an electric potential
between IDT electrodes and the electrostatic field. There is a field with the elliptically
polarized component determining an arising acoustic wave as a result of the superposition
of the source field and the complementary subfield. The acoustic wave after the reflection
effects on IDTs and brings to the distribution of electric charges due to the direct
piezoelectric effect between IDT electrodes and to the generation of an electromagnetic
signal. The SAW velocity and frequency this one are changed depending on different
conditions of the propagation medium. The SAW propagates from IDTs in the direction of
