41 Degree lithium niobate: A study of harmonics

Various orientations of Lithium Niobate (LNB) have been used for Surface Acoustic Wave (SAW) devices. This study used 41 degree LNB in order to study the harmonics, loss characteristics, and the characteristics of damping intervening transducers on the free surface LNB. The original objective of this study was to determine how the loss characteristics of the harmonics varied with frequency over the extended frequency region from 40 MHz to 1500 MHz. The secondary objective was the damping of intervening transducers over the frequency region from 40 MHz to over 700 MHz. The frequency characteristics were determined using a double electrode transducer on the 41 degree LNB with a total of 8 transducers. The transducer had electrodes of 15 micron spaces and 10 micron gaps giving a total wavelength electrode spacing of 100 microns. There were 10.5 wavelengths at the fundamental. The study also included various conditions for intervening transducers which allowed the comparison of loss characteristics up to 700 MHz. The results of the study allowed the assignment of an average loss to each frequency. The loss increased with frequency in a systematic manner but the results at certain frequencies were higher loss than anticipated. This resulted in the re-evaluation of the modes of the transducer. Also above 1300 MHz the loss in the SAW mode became lower. As predicted, the PSAW mode loss is lower for the free surface of the 41° LNB.