REVERSIBLE NATURAL-DIRECTIVITY SURFACE-ACOUSTIC-WAVE TRANSDUCER (DESIGN VERSIONS) Russian patent published in 2000 - IPC

FIELD: radio electronics; intermediate- and carrier-frequency filters for signal discrimination in radiophones, pagers, mobile communication systems, etc. SUBSTANCE: sending electric signal to unidirectional transducer incorporating elementary sections of anti-phase exciting electrodes and reflecting electrode excites surface acoustic waves in piezoelectric substrate which propagate in forward and reverse directions. Natural direction of waves is ensured due to the fact that substrate is made of single-crystal chip wherein mechanical and electromagnetic components of propagating surface acoustic waves are relatively shifted through 0 < Δϕ < ±90^o. First design version has widths b₁ and b₃ for first and second exciting electrodes chosen from expressions λ/16 < b₁ < λ/8, and λ/6 < b₃ λ/3, respectively. and width of reflecting electrode found from expression λ/6 < b₅ < λ/3. Distance between adjacent edges of first and second exciting electrodes is chosen from expression λ/6 < b₂ < λ/6 and that between adjacent edges of second exciting electrode and reflecting electrode is chosen from expression λ/6 < b₄ < λ/3, where λ is length of surface acoustic wave at intermediate frequency. Second design version of transducer is characterized in that width of exciting electrodes is found between λ/16 < b₁ < λ/6 and λ/6 < b₃ < 3λ/8 and that of reflecting electrode is chosen from expression λ/6 < b₃ < 3λ/8 at gaps λ/16 < b₂ < λ/6 and λ/24 < b₄ < λ/6. Mentioned relations cause displacement of acoustic surface wave relative reflection center through distance ±λ/8 at given Δϕ thereby raising efficiency of surface acoustic wave conversion by 20% at the same time increasing natural directivity of radiation in reverse direction. EFFECT: reduced insertion loss of transducer and of filter using this transducer. 4 cl, 8 dwg