WIDEBAND TWO-MODE LEAKY SURFACE ACOUSTIC WAVE FILTER WITH NON-EQUIDISTANT ELECTRODES OF TRANSDUCERS AND REFLECTING GRATINGS
Victor S. Orlov, Moscow Technical University of Communication and Informatics, Moscow, Russia, email@example.com
Asymmetric magnitude response with flat high frequency slop and «shoulder» with level -(10-15) dB appears by traditional section of two mode filters because of leaky surface acoustic wave (SAW) internal reflection from transducers electrodes. Additionally, gaps between input and output transducers represent like acoustical heterogeneities for leaky SAW. As result , ripples of magnitude response in pass band are increased and additional losses appear because of transformation of leaky SAWs in balk acoustic waves ( BAW). Structure of ultra-high frequency (UHF) two cascade leaky SAW filter is described , which allows to degrease an influence of indicated effects significantly. At frequency 1310 MHz such structure allows to achieve wide pass band width about BW3=8,7%, close to as much as possible, realize high selectivity 52-56 dB near pass band and no less 43-48 dB in wide frequency range before 3.0 GHz. «Shoulder» suppression before 52-54 dB at high frequency slop is obtained it two wais. First , via application of reflection gratings between transducers like additional acoustical frequency selective elements. Second, via modulation of pitches of groups electrodes in transducers and reflecting gratings with next optimization these pitches. Parallel connection of sells in each cascade is used for insertion loss decreasing. In contrast to analogues, standard technology , wafer and electrode materials are used. As result, described structure may be used like basic structure for leaky filters.
Keywords: leaky surface acoustic wave, two mode filter, sell, cascade, interdigital transducers, reflecting grating, insertion loss, selectivity.
1. Morita T., Watanabe Y., M. Tanaka M. and Nawazawa Y. Wideband Low Loss Double Mode SAW Filters. IEEE 1992 Ultrasonics Symposium Proc. Pp. 95-104.
2. Campbell C.K. (1995). Longitudinal-Mode Leaky SAW Resonator Filters on 64 deg Y-X Lithium Niobate. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, vol. 42, No. 5. Pp.883-888.
3. Ivanov P.G., Makarov V.M., Orlov V.S., Shvets V.B. Wideband Low Loss SAW Filters for Telecommunication and Mobile Radio Application. IEEE 1996 Ultrasonics Symposium Proc. Pp. 61-64.
4. Hashimoto K., Miyamoto T., Shimada K., Omori T. and Yamaguchi M. A Wideband Multi-Mode SAW Filter Employing Pitch Modulated IDTs on Cu-Grating/15o YX-LiNbO3- Substrate Structure. IEEE 2009International Ultrasonics Symposium Proc. Pp. 915-918.
5. Sharif M.A., Lambert C., Chen D.P. and Hartmann C.S. Network Coupled, High Performance SAW Resonator filters. IEEE 1994 Ultrasonics Symposium Proc.1994. Pp.135-138.
6. Takamine Y. Longitudinally Coupled Resonator Type SAW Filter with an IDT having a Narrow Pitch Position. US Patent No.: US 6,583,691 B2 Date of Patent: Jun. 24, 2003. Int. Cl. HO3H 9/64.
7. Orlov V.S. Modified Model of Equivalent Schemes for Simulation of Surface Acoustic Wave Devices. y2002, Pp.64. Official site www.saw-filters.ru of Acoustoelectronic Filters Laboratory, MTUCI. Item «Reviews and Investigations». Free Access html://saw-filters.ru/. Date of Application: January 2019. (in Russian)
8. Meltaus J., Hong S. S., Holmgren O., Kokkonen K., and Plessky V.P. (2007). Double-Resonance SAW Filters. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 54, no 3. Pp. 659-667.
9. Orlov V.S., Bondarenko V.S. (1984). Filters on Surface Acoustic Waves. Moscow: Radio and Communication. 276 pp. (in Russian)
10. Makarov V.M., Ivanov P.G., Danilov A.L., Zaya V.G. (2008). Surface Acoustic Wave Resonator Filters Based on Dispersive Transducers. Radiotekhnika and Elektronika, vol. 53, no. 3. Pp.377-382.
11. Meltaus J., Hemeleinen P., Salomaa M.M. and Plessky V.P. Genetic Optimization Algorithms in the Design of Coupled SAW Filters. IEEE 2004 International Ultrasonics Symposium Proc. Pp. 915-918.
12. Tagawa K. Multi-Stage Design of DMS Filters with Free & Freeze Method. 6th WSEAS 2006 International Conference on Applied Computer Science Proc. Pp. 508-513.
13. Rusakov A.N., Orlov V.S., Chao B. and Lee V. Application of Modified P-Matrix Model to the Simulation of Radio Frequency LSAW Filters. IEEE 2001 Ultrasonics Symposium Proc. Pp.7-11.
14. Wang W., Wu H. High Selectivity SAW DMS Filter with In-between Shorted-gratings. IEEE 2010 Ultrasonics Symposium Proc. Pp. 1263-1266.
15. Loseu A. Double Mode SAW Filters with Improved Selectivity. IEEE 2000 Ultrasonics Symposium Proc. Pp. 95-98.
16. Kovacs G., Sauer W., and Bauer T. DMS Filter with Reduced Resistive Losses. IEEE 2004 Ultrasonics Symposium Proc. Pp. 294-297.
Information about author:
Victor S. Orlov, Moscow Technical University of Communication and Informatics, Moscow, Russia