[射频]Theory and Application of Passive SAW Radio Transponders as Sensors

ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 45, no. 5, september 1998 1281 iL/
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Theory and Application of Passive SAW Radio WQ|:TLQ  
Transponders as Sensors %nA})nA7=  
Leonhard Reindl, Member, IEEE, Gerd Scholl, Member, IEEE, Thomas Ostertag, 1gI7$y+?  
Associate Member, IEEE, Holger Scherr, Ulrich Wol, and Frank Schmidt CH++3i2&  
Abstract|Surface acoustic wave (SAW) radio transponders 6BE
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make it possible to read identication codes or measurement )p&g!qA  
values from a remote location. The decisive advantage u{1R=ML  
of these SAW transponders lies in their passive *k?:k78L  
operation (i.e., no power-supply), and in the possibility of F72#vS j  
wireless installation at particularly inaccessible locations. ChBf:`e  
The passive SAW transponders are maintenance free. F.s$Y+c!6  
Identication marks respond to an interrogation signal 7iB!Uuc  
with their nonchanging identication pattern. In wireless z]7 WC  
SAW sensors the physical or chemical properties to be detected VRo&1:  
change the propagation characteristics of the SAW. c:Ua\$)u3,  
SAWradio transponders are advantageously placed on moving "be\%W+<  
or rotating parts and in hazardous environments such ]m1fo'  
as contaminated or high voltage areas. They also can be \!KE_7HRu  
used for contactless measurements in high vacuum process w,|@e_|J  
chambers, under concrete, extreme heat, or strong radioactive d0J/"<  
radiation, where the use of conventional sensors UmKE]1Yw4r  
is complicated, dangerous, or expensive. In this paper we Ii
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discuss the principles of wireless passive SAW transponders _[:6.oNjIe  
and present a radio frequency interr .. *,u3Wm|7  
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