Longitudinal leaky SAW resonators and filters on YZ-LiNbO3.

The high-phase velocity (above 6100 m/s in an aluminum (Al) grating on lithium niobate (LiNbOs)) of the longitudinal leaky surface acoustic wave (SAW) (LLSAW) mode makes it attractive for application in high-frequency SAW ladder filters in the 2-5 GHz range. We investigate the dependence of one-port synchronous LLSAW resonator performance on YZ-LiNbO3 on the metallization thickness and metallization ratio, both experimentally and theoretically. Our results indicate a strong dependence of the Q factor and resonance frequency on the aluminum thickness, with the optimal thickness that produces the highest Q values being about 8%. The optimal thickness increases with the metallization ratio. The observed behavior is interpreted with the help of simulations using a combined finite element method (FEM)/boundary element method (BEM) technique. As an application, bandpass filters have been fabricated in the 2.8 GHz frequency regime, based on LLSAWs. The synchronous resonators constituting the ladder filters operate in the fundamental mode. The filters feature low insertion losses below 3 dB and wide relative passbands of 4.5-5%.

[1]  Clemens Ruppel,et al.  Improved material constants for LiNbO/sub 3/ and LiTaO/sub 3/ , 1990, IEEE Symposium on Ultrasonics.

[2]  M. Hikita,et al.  Propagation characteristics of longitudinal leaky SAW in Al-grating structure , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[3]  T. Sato,et al.  Propagation of longitudinal leaky surface waves under periodic metal grating structure on lithium tetraborate , 1998, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[4]  V. I. Grigorievski.  Fast leaky surface acoustic waves on lithium niobate and lithium tantalate , 2000, 2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121).

[5]  J. Koskela,et al.  SAW/LSAW COM parameter extraction from computer experiments with harmonic admittance of a periodic array of electrodes , 1999, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[6]  Leaky SAW in an isotropic substrate with thick electrodes , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[7]  J. Kaitila,et al.  Thin film bulk acoustic wave filter , 2002, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  Marc Solal,et al.  Numerical methods for SAW propagation characterization , 1998, 1998 IEEE Ultrasonics Symposium. Proceedings (Cat. No. 98CH36102).

[9]  T. Sato,et al.  SAW device applications of longitudinal leaky surface waves on lithium tetraborate , 1998, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[10]  Alexei A. Maradudin,et al.  Leaky surface‐elastic waves on both flat and strongly corrugated surfaces for isotropic, nondissipative media , 1983 .

[11]  N. Naumenko,et al.  High-velocity surface acoustic waves in diamond and sapphire with zinc oxide film , 1999 .

[12]  T. Makkonen,et al.  Existence of harmonic metal thickness mode propagation for longitudinal leaky waves , 2004, IEEE Ultrasonics Symposium, 2004.

[13]  K. Shibata,et al.  1.9-GHz-Band Surface Acoustic Wave Device Using Second Leaky Mode on LiTaO3 , 1996 .

[14]  T. Makkonen,et al.  Surface-acoustic-wave devices for the 2.5–5 GHz frequency range based on longitudinal leaky waves , 2003 .

[15]  M. Solal,et al.  Fundamental mode 5 GHz surface-acoustic-wave filters using optical lithography , 2003 .

[16]  T. Sato,et al.  Propagation properties of longitudinal leaky surface waves on lithium tetraborate , 1998, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[17]  M. P. D. Cunha.  High velocity pseudo surface waves (HVPSAW): further insight , 1996 .

[18]  Didenko,et al.  "Fast" quasilongitudinal sagittally polarized surface waves in layer-substrate structures , 2000, The Journal of the Acoustical Society of America.

[19]  L. Kopp,et al.  FEM/BEM simulation and experimental study of LLSAW resonator characteristics on YZ-LiNbO/sub 3/ , 2002, 2002 IEEE Ultrasonics Symposium, 2002. Proceedings..

[20]  F. Hickernell,et al.  The experimental and theoretical characterization of the SAW propagation properties for zinc oxide films on silicon carbide , 2000, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[21]  R. Holland,et al.  Representation of Dielectric, Elastic, and Piezoelectric Losses by Complex Coefficients , 1967, IEEE Transactions on Sonics and Ultrasonics.