Lithium Niobate Thin Film Based A₁ Mode Resonators with Frequency up to 16 Ghz and Electromechanical Coupling Factor Near 35%

The 5G or emerging sub-6G systems have turned to millimeter wave (mmw) frequency range with large bandwidth, so it is urgent to develop suitable filter to meet the spectrum requirements. In order to make acoustic platform still competitive in future communication, the first-order antisymmetric (A(1)) lamb mode resonators were constructed on thin 128 degrees Y-X LiNbO3 (LN) film, while the high crystal quality and flat surface were ensured. By analyzing the propagation characteristics through calculation and experiment, it is found that the A(1) mode not only possesses high electromechanical coupling factor (K-2) around 35% but also can obtain frequency enhancement by thinning LN film. The measurement results show that as the LN film is trimmed to 110 nm, the center frequency of resonator can be extended 16.9 GHz, while the K-2 is as high as 34.2%. The achieved specifications demonstrate the potential of the acoustic platform to be applied in the mmw systems.