Kadota Michio, Ishii Yoshimi, Tanaka Shuji
IEEE Trans Ultrason Ferroelectr Freq Control. 2021 May;68(5):1955-1964. doi: 10.1109/TUFFC.2020.3039471. Epub 2021 Apr 26.
This article reports a new concept of surface-acoustic-wave (SAW) resonator, which uses shear horizontal (SH) wave confined in a thin LiTaO (LT) layer supported by a quartz (Qz) substrate. The LT layer is 35-50°YX LT, and the quartz substrate is 35-60°Y90°X Qz. A negative temperature coefficient of frequency (TCF) of the SH SAW in the LT layer is compensated by the quartz substrate, which shows a wide range of positive TCF depending on the crystalline orientation. Excellent TCFs of 2 and -10 ppm/°C were measured for the series and parallel resonance frequencies, respectively. The strong confinement of the SH SAW in the LT layer results in the best level of resonance characteristics ever reported. The measured impedance ratio reached 84 dB. On the other hand, spurious waves other than the SH SAW are not confined in the LT layer due to the unique properties of quartz, which results in spurious-free characteristics throughout a wide frequency range.
本文报道了一种表面声波（SAW）谐振器的新概念，它利用限制在由石英（Qz）衬底支撑的薄钽酸锂（LT）层中的水平剪切（SH）波。LT层为35 - 50°YX LT，石英衬底为35 - 60°Y90°X Qz。LT层中SH SAW的负频率温度系数（TCF）由石英衬底补偿，石英衬底根据晶体取向显示出宽范围的正TCF。对于串联和并联谐振频率，分别测得优异的TCF为2 ppm/°C和 - 10 ppm/°C。SH SAW在LT层中的强限制导致了有史以来报道的最佳谐振特性水平。测得的阻抗比达到84 dB。另一方面，由于石英的独特特性，除SH SAW之外的杂散波不会限制在LT层中，这导致在很宽的频率范围内具有无杂散特性。
