[其它]Extraction of the SAW Attenuation Parameter in Periodic Reflecting Gratings

ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 52, no. 1, january 2005 111 hgzNEx%^q  
Extraction of the SAW Attenuation Parameter ~I9o*cq  
in Periodic Reflecting Gratings p&5>j\uJ1&  
Saku Lehtonen, Victor P. Plessky, Senior Member, IEEE, Clinton S. Hartmann, Member, IEEE, and /h{Rf,H  
Martti M. Salomaa, Member, IEEE FD&^nJ_{  
Abstract—In this paper, the extraction of the couplingof- Pf<yLT]  
modes (COM) model attenuation parameter 􀀀 in a finite z@w}+fYO  
grating is considered. We use test structures comprising W/b)OlG"2  
identical transmitting and receiving transducers and a grating #ti%hm  
centered in the acoustic channel along the propagation aEh9za  
direction of the surface acoustic wave (SAW). The extraction l5~O}`gfh  
procedure proposed is based on studying the magnitude +S[3HX7H  
of the ratio of the reflection and transmission coefficients 4=EA3`l  
of the grating, R/T, obtained through time gating 7!h> < sx  
from the S parameter measurements of the test devices. In G "!v)o  
particular, we found that the level of the notches of R/T directly BFg&@7.X  
depends on the attenuation of SAW in the grating. A $d!Vxm  
simple closed-form expression for the attenuation normalized -(>Ch>O  
to the grating length, 􀀀0, depending on the characteristics m(d|TwG{  
of jRTj, is gi .. Ok|Dh;1_  
sHMO9{[7H  

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