FEATURES OF TEMPERATURE COEFFICIENT OF FREQUENCY SAW LONGITUDINALLY-COUPLED RESONATOR FILTERS BASED ON LITHIUM TANTALATE YXL/42° CUT
Ilya A. Tourkine, Moscow Technical University of Communication and Informatics, Moscow, Russia, tourezkiy@gmail.com
Abstract
Temperature coefficient of frequency (TCF) is a very significant parameter of surface acoustic wave (SAW) filters. High temperature stability let use SAW-filters in more special radio electronic applications (for example: military, special, aviation or space), in case of strict requirements where operating temperature range can reach more than 140°. SAW filters meet these requirements due to the low absolute values temperature coefficient of delay (TCD) of the monocrystal cut, that is used during production process. Also it depends on the thickness and the coefficient of metallization of the interdigital transducers (IDT) and varies from tenths to tens ppm/°C.
This article describes an investigation of SAW longitudinally-coupled resonator filters (LCRF) frequency response behavior at wide temperature range (-60°Ñ +85°Ñ), special attention is paid to measurement technique; presents a large amount of experimental data
(18 samples of 6 filters by frequency 465, 607, 836, 1200, 1590 and 2067 MHz), the real average TCF of lithium tantalate (LiTaO3) yxl/42° cut based filters, reference values and metallization thickness is shown. À regular difference between low and high limit frequencies TCF is also presented; built the averaged (logarithmical approximation method is used) dependence of TCF on frequency. There are given main possible reasons for this difference.
Keywords: surface acoustic wave filters, Longitudinally-Coupled Resonator Filter, temperature coefficient of delay, lithium tantalite.
References
1. G. Kovacs, M. Anhorn, H.E. Engan, G. Visintini, and C.C.W. Ruppel, (1990). “Improved material constants for LiNbO3 and LiTaO3,” Proc. IEEE Ultrasonics Symp. Vol. 1, pp. 435-438.
2. David P. Morgan, (2004). Idealised analysis of saw longitudinally coupled resonator (LCR) filters, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (Vol. 51, Issue: 9, Sept. 2004), ðð. 1165-1170.
3. Orlov V.S. (2015). Miniature longitudinally coupled resonator surface acoustic wave filters with “flip-chip” assembly technology for navigation systems GLONASS-GPS. T-Comm. Vol 9. No.4, pð. 40-50. (in Russian)
4. Orlov V.S. (2016). The ladder resonator filters on surface acoustic waves for receivers of navigation systems. T-Comm. Vol. 10. No.5, pp. 8-16. (in Russian)
5. Tourkine I.A. (2013). The automation of complex measurements electrical parameters of saw-filters. T-Comm. No.5, pp. 45-48.
6. Surface acoustic Wave Filters. Official site www.saw-filters.ru, [Electronic Recourse] of MTUCI Filters Laboratory. Access conditions: html://saw-filters.ru/. Free (date of communication: 10.09.2019). (in Russian)
Information about author:
Ilya A. Tourkine, candidate of sciences, head of R&D acoustoelectronic laboratory, Moscow Technical University of Communication and Informatics, Moscow, Russia