Considerations for dynamic temperature compensation of wideband ladder-type SAW filter

Because of their excellent features such as small size, wide bandwidth, and low insertion loss, ladder-type filters based on surface acoustic wave (SAW) technology have been widely used as radio-frequency (RF) filters in mobile communications. We can realize wide bandwidth and low insertion loss in ladder-type SAW filters on a Cu-grating/15°LiNbO3 substrate structure. On the other hand, it is said that wide-bandwidth filters have poor temperature characteristics. Therefore, this paper discusses dynamic temperature compensation for wideband ladder-type SAW filters. First, we investigate how wide tunability is achievable using variable capacitors connected in parallel and/or series to SAW resonators in the filter configuration. Second, we measured the temperature characteristics of the resonator. Finally, we simulated temperature compensation in wideband ladder-type SAW filters. As a result, we were able to compensate the change of the characteristics with the ladder-type SAW filter connected using variable capacitors. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(4): 61–66, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10420