Design and simulation of dual-mode structure of two-dimensional-mode resonators based on AIN film
Two-dimensional-mode resonators(2DMR)based on aluminum nitride(AlN)piezoelectric thin films have attracted extensive attention in the industry due to their high effective electromechanical coupling coefficient keff and compatibility with integrated circuit processes.However,traditional 2DMRs have only studied a single resonant mode,which cannot meet the needs of multimode wireless communication systems.To address this issue,a dual-mode two-dimensional-mode(2DM)resonator for 2.6-3.4 GHz has been proposed.By reasonably designing the electrode width and period,the quality factor Q and k2eff of the two modes are made comparable,effectively exciting the S1 mode and the higher-order S1 mode.The finite element method was used to analyze the impact of piezoelectric material thick-ness and comb electrode structure on the dual-mode resonant frequency and k2eff of the 2DMR.The resonant frequency of the S1 mode is primarily influenced by the thickness of the piezoelectric material,while the resonant frequency of the higher-order S1 mode is also sensitive to the width of the metal electrodes.Based on the combined effects of the d33 and d31 piezoelectric coefficients in the AlN piezoelectric thin film,the k2eff of the two modes in the designed 2DMR reached 3.1％and 3.6％,respectively.Subsequently,a dual-band bandpass filter with a 50 Ω impedance matching network was designed based on the S1 mode and higher-order S1 mode resonances for their spurious-free and high electromechanical coupling performance,improving the device's out-of-band suppression by increasing the order.The filter's two transmission bands are adjacent,without in-band ripple and with sharp roll-off,centered at 2.852 and 3.082 GHz,respectively,with insertion losses of 2.0 and 1.9 dB,and fractional bandwidths of 29 and 39 MHz,respectively.The research results demonstrate the great application potential of this dual-mode 2DMR struc-ture design in RF front-ends.
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