| 摘要 |
radio electronics; intermediate- and carrier-frequency filters of radiophones, pagers, mobile communication systems, etc. SUBSTANCE: supplying electric signal to unidirectional transducer incorporating elementary sections of counter- phase exciting electrodes and reflecting electrode excites surface acoustic waves in piezoelectric substrate which propagate in forward and reverse directions. Substrate is made of single chip where mechanical and electromagnetic components of propagating surface acoustic wave are relatively shifted through DELTAϕ ≈ ±45°, so as to ensure natural directivity of radiation. Width of first and second exciting electrodes in each elementary section b1= lambda/8 and b3= 3lambda/16, respectively and reflecting electrode width b5= 3lambda/16. Distance between adjacent edges of first and second exciting electrodes b2= lambda/8 and distance between adjacent edges of second exciting electrode and reflecting electrode b4= lambda/4, where lambda is length of surface acoustic wave at midpoint. Width of exciting electrodes in second design version b1= lambda/8 and b3= lambda/4 and that of reflecting electrode b5= lambda/4 at gaps b2= b4= lambda/8. Under mentioned conditions, center of excitation of surface acoustic waves is offset relative to their center of reflection through ±lambda/8 which raises efficiency of surface acoustic wave conversion by 20% at the same time enhancing natural directivity of waves in reverse direction. EFFECT: reduced insertion loss of transducer and associated filter. 2 cl, 7 dwg
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