Golden Age of Acoustic Resonators & Filters

For many years, various specialized filter technologies catered to the niche RF market. Even with the advent of mobile phones in the late 80s, filter technology was slow to respond or adapt. Early ‘brick’ phones supported only one or two radio bands using hand-crafted ceramic filters. Although these filters were the size of a child’s finger, they worked fine for the mobile application.

Demand for acoustic SAW (Surface Acoustic Wave) and FBAR (Free-standing Bulk Acoustic Wave) filter technology started small. While these parts were several orders of magnitude smaller than ceramic filters and offered better performance, they cost considerably more - doing little at the time to excite investors on Wall Street.

However, this changed dramatically in the second decade of the new millennium. As smartphone adoption accelerated and expensive devices began supporting multiple frequency bands (now around 100), the number of radio frequency bands inside each device exploded. The math was simple: more smartphones with multiple radio bands meant many times more filters.

Only one fundamental technology - acoustic devices - can meet the extensive list of RF filter "musts" in mobile phones: low insertion loss in the radio band, large rejection of extraneous RF noise, large power density handling, excellent linearity, minuscule size, and relatively low cost.

Today, the RF Radio Front End (RFFE) module is one of the most expensive components in a smartphone, and the multiple filters inside are among its highest-cost elements. Filters define the cost, size, and performance of these modules.

Currently, there are two competing acoustic-based technologies for high-performance filters:  Surface Acoustic Wave (SAW) and Free-standing Bulk Acoustic Wave (FBAR) devices. FBAR originated at HP Labs in the early 90s, moved to Agilent, and finally to Avago, which later became Broadcom. Hock Tan, now CEO of Broadcom, leveraged this “FBAR Growth Engine” to finance a massive acquisition spree of technology companies, including Broadcom and VMware, helping build Broadcom into a trillion-dollar company.

This talk will begin with the background and motivation behind the explosion in filter demand, then explore potential new markets and technologies just “over the horizon” that could be created using acoustic-based devices. Throughout the presentation, the speaker will provide simple technical explanations of how acoustic devices work.

Speaker: Rich Ruby, Broadcom

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