Design of a New Step-like Frame FBAR for Suppression of Spurious Resonances

Film bulk acoustic wave resonators (FBARs) are of great interest for wireless applications due to its inherent advantages at microwave frequencies. However, the presence of spurious modes near the main resonance degrades the performance of resonators and requires development of new methods to suppress such unwanted modes. Different techniques are used to suppress these spurious modes. In this paper, we present design of a new step-like frame structure film bulk acoustic wave resonator operating near 1.5 GHz. The simulated results are compared with simple frame-like structure. The spurious resonances are eliminated effectively and smooth pass band is obtained with effective coupling coefficient of 5.68 % and quality factor of 1800. The equivalent electrical mBVD model of the FBAR based on impedance response is also presented. These highly smooth phase response and passband skirt steepness resonators are most demanding for the design of low cost, small size and high performance filters, duplexers and oscillators for wireless systems.

[1]  R. Aigner.  MEMS in RF Filter Applications: Thin‐film Bulk Acoustic Wave Technology , 2003 .

[2]  Jiunn-Horng Lee,et al.  Optimization of frame-like film bulk acoustic resonators for suppression of spurious lateral modes using finite element method , 2004, IEEE Ultrasonics Symposium, 2004.

[3]  Humberto Campanella,et al.  Acoustic Wave and Electromechanical Resonators: Concept to Key Applications , 2010 .

[4]  Steven Mahon,et al.  Bulk Acoustic Wave Devices - Why, How, and Where They are Going , 2007 .

[5]  O. Menendez,et al.  Electric Equivalent Circuit for the Thickened Edge Load Solution in a Bulk Acoustic Wave Resonator , 2010 .

[6]  P. Muralt,et al.  Bandpass filters for 8 GHz using solidly mounted bulk acoustic wave resonators , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[7]  R. Aigner,et al.  Spurious resonance free bulk acoustic wave resonators , 2003, IEEE Symposium on Ultrasonics, 2003.

[8]  N. Yanase,et al.  P2G-4 Suppression of Acoustic Energy Leakage in FBARs with Al Bottom Electrode: FEM Simulation and Experimental Results , 2007, 2007 IEEE Ultrasonics Symposium Proceedings.

[9]  Sheng-Yuan Lee.  Optimum resonant conditions of stepped impedance resonators , 2005, 2005 European Microwave Conference.

[10]  Akira Ishikawa,et al.  About the Authors , 2001 .

[11]  Wenxia Yang,et al.  Spurious wave suppression in BAW resonators with frame-like airgap , 2010, 2010 IEEE International Frequency Control Symposium.

[12]  J. Bjurstrom,et al.  Suppression of spurious lateral modes in thickness-excited FBAR resonators , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.