Lu Ruochen, Yang Yansong, Li Ming-Huang, Gong Songbin
IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Jul;67(7):1448-1461. doi: 10.1109/TUFFC.2020.2971196. Epub 2020 Feb 3.
We present the first group of GHz low-loss acoustic radio frequency (RF) couplers using the fundamental symmetric (S0) mode in X-cut lithium niobate thin films. The demonstrated multistrip couplers (MSCs) significantly surpass the insertion loss (IL) and the operating frequency of the previous works in more compact structures, thanks to the large electromechanical coupling and low loss of S0 in lithium niobate. The design space of S0 MSCs is first explored. Devices with different coupling factors are fabricated using different numbers of strips. Based on the S0 testbed with an IL of 4.5 dB at 1 GHz, the hybrid coupler shows an IL of 7.5 dB, while the track changer shows an IL of 5.1 dB, over a 3-dB fractional bandwidth of 8%. Couplers at different frequencies (between 0.75 and 1.55 GHz) are also investigated. Upon further optimizations, the S0 MSC platform can potentially enable low-loss wideband signal processing functions toward an RF acoustic component kit.
我们展示了首批在X切铌酸锂薄膜中使用基本对称（S0）模式的千兆赫兹低损耗声学射频（RF）耦合器。由于铌酸锂中S0的机电耦合系数大且损耗低，所展示的多带耦合器（MSC）在更紧凑的结构中显著超越了以往工作的插入损耗（IL）和工作频率。首次探索了S0 MSC的设计空间。使用不同数量的条带制造了具有不同耦合因子的器件。基于在1 GHz时IL为4.5 dB的S0测试平台，混合耦合器在8%的3 dB分数带宽上显示出7.5 dB的IL，而轨道变换器显示出5.1 dB的IL。还研究了不同频率（0.75至1.55 GHz之间）的耦合器。经过进一步优化，S0 MSC平台有望实现面向射频声学组件套件的低损耗宽带信号处理功能。
