Or, the substrate may further include {HEAD ~ an absorber} for absorbing the surface acoustic wave propagated in {TAIL ~ the surface acoustic wave propagation region} 
Or , the substrate may further include { HEAD ~ an absorber } for absorbing the surface acoustic wave propagated in { TAIL ~ the surface acoustic wave propagation region }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL