Low-loss NSPUDT SAW filter without reversing the directivity of NSPUDT

This paper presents the low-loss Natural Single Phase Unidirectional Transducer (NSPUDT) SAW filter localizing an acoustic energy without reversing the directivity of NSPUDT. An asymmetric ST (X±25°) quartz crystal orientation was used for the piezoelectric substrate where a SAW unidirectional radiation and receiving is possible by an usual transducer with an electrode width of λ/4. In a filter design the inclined NSPUDTs are used and a SAW transmission between them is provided by a single reflection of SAW from a polished edge of a piezoelectric substrate. An experimental sample of the SAW filter at a center frequency of 54.1 MHz showed an insertion loss of 7.5 dB and low amplitude ripple within the passband with the use of the matching LC-elements.