| 摘 要： | According to theoretical prediction,the distribution of acoustic wave power flux launched inboth directions by the linear FM interdigital transducer(IDT)is a symmetrical in nature.Methodsof acousto-optic diffraction have been employed to detect acoustic field distrbution of linear FM IDT.Three unapodized linear FM IDT which have different parameters are examined.These transducersare formed with aluminum electrodes deposited on the piezoelectric substrates of Y-cut Z-pro-pagating lithium niobate.Expermental results show that surface acoustic wave(SAW)power fluxradiated from the high frequency portion of linear FM interdigital transducer is stronger than thatfrom the low frequency one.The asymmetry increases with the number of the effective fingerpairs.In general,the asymmetry increases with the exciting frequency but the relation betweenthem is not monotonic.Based on the equivalent circuit,numerical evaluations of the asymmetricdistribution have been made.The theoretical curves essentially agree with the
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