At the substrate level, the change can be seen compared to a standard SAW filter, with the use of a lithium niobate substrate that provides better acoustic wave velocity (see Figure 3).
However, the process adds features to enhance the isolation, by adding thermo-compensation layers. TC-SAW technology still uses a thin film deposition manufacturing process. TC-SAW filters have been built specifically for these cases. The gap between some frequency bands is very tight, so performance drift, mainly due to thermal changes on the structure, must be controlled to avoid filtering overlaps.
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Source: System Plus Consulting, 2020.įor more challenging bands, TC-SAW filters are required and fewer companies supply these. The result of such a simple process is a very low cost device that fits low frequency filtering requirements but is not suitable for selected high frequencies like band 8, 26 or 13 on the LTE protocol, or better performance demanded by 5G.įigure 3 Acoustic wave filter construction overview. This standard technology is usually based on metal electrode (aluminum, titanium, gold, copper) forming the interdigital transducer (IDT) on a single crystal piezoelectric like lithium tantalate (LT) as shown in Figure 3. Wisol, a Korean-based company that provides discrete filters and modules to OEMs like Samsung, has supplied a module with a single die SAW duplexer designed by Resonant for a low-end smartphone, the XCover 4. This has spawned new companies, like Resonant, that provide simulation tools to enable fabless companies to quickly develop filters and foundry services to manufacture them.
Several Asian-based companies have risen over the past few years to introduce their own technology at a low cost, to be integrated into the Chinese domestic market in discrete models like Vivo, Huawei, etc. As SAW filters use lateral propagation of the high frequency waves, it only requires simple manufacturing processes. Source: System Plus Consulting, 2020.Īt low frequencies, SAW filter technology is well known and small companies are competing with the market leaders to create an alternative filter ecosystem. The fourth is an Asian-based company, Murata.įigure 2 Acoustic wave filter market players and their technologies. More than half of them are U.S.-based companies: Qorvo and Skyworks, that only provide TC-SAW components using in-house design, and Qualcomm, with a complete portfolio from legacy SAW to SMR-BAW filters. For TC-SAW, the number of manufacturers drops to four. For standard SAW, eight companies that supply such devices are included in a comparative report shown in Figure 2. Two main technologies split the market for piezoelectric filters, BAW and SAW. The filters based on this technology rely on the electro-mechanical effect of the material to propagate the RF signal and filter it at a certain frequency. The most suitable substrate technology for smartphones and other small form factor applications is a piezoelectric material. In the filter family, the substrate is the first means of differentiation between the players. In this article, the acoustic filter technology currently available on the market is described including the costs for both SAW and BAW devices followed by an overview of the upcoming technologies for future applications, including new structures and costs. In the middle frequency ranges, SAW companies are looking for cost effective solutions with high performance: temperature-compensated SAW (TC-SAW) filters, thin film SAW (TF-SAW), etc.With the rise of 5G and Wi-Fi 6E, almost all market leaders are looking for BAW solutions.Market leaders, with the development of new technology, are increasing the frequency range of well know devices such as SAW and film bulk acoustic resonator (FBAR)-BAW filters.U.S.-based companies mainly offer high performance SAW filters.Asian-based companies are offering their own SAW technology which is lower cost compared to other competitors.This situation is no longer the case in the market as several companies have developed technologies that will disrupt the filter market. Figure 1 Acoustic wave filter technology in the 5G NR landscape.
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