Self-similarity is a characteristic found in many physical, natural, and human-made systems. In short, it describes a class of structures or behaviors that are at least partially-invariant to time or scale. Thus, these structures or behaviors appear similar in various mathematical ways whether viewed in small or large samples. A well-known class of self-similar objects are fractals, but self-similarity is a broader concept and can be found in clouds, waves, certain types of plants, snowflakes, coastlines, and Internet traffic and latency measurements, as well as numerous other areas.
Shure's U.S. Patent No. 9,565,493 describes various types of "self-similar" microphone arrangements for drop ceilings. The specification of the '493 patent states that such arrangements "include a plurality of microphone transducers selectively positioned in a self-similar or fractal-like configuration, or constellation" and that "this physical configuration can be achieved by arranging the microphones in concentric rings, which allows the array microphone to have equivalent beamwidth performance at any given look angle in a three-dimensional (e.g., X-Y-Z space)."
ClearOne filed a petition for inter partes review (IPR) of the '493 patent. It was instituted and during the proceeding Shure moved to amend one of the claims to recite:
A microphone assembly comprising:
an array microphone comprising a plurality of microphones arranged in a self-similar configuration . . .
The Patent Trial and Appeal Board (PTAB) panel granted the motion and noted that "a skilled artisan would understand 'self-similar' to have had a well-known meaning and include the specification's disclosure of fractal-like configurations or constellations, which does not create an ambiguity." The PTAB's decision was based on the specification, extrinsic dictionary definitions, and expert testimony. ClearOne appealed, contending (among other issues) that the claim as amended was indefinite.
On review, the Federal Circuit set forth the principles of definiteness as being that "claims, viewed in light of the specification and prosecution history, [must] inform those skilled in the art about the scope of the invention with reasonable certainty." Further, "[e]xtrinsic evidence may help identify the scope of the claims."
The Court rapidly agreed with the PTAB. It observed that the specification "discloses an embodiment having a plurality of MEMS microphones . . . arranged in a self-similar or repeating configuration comprising concentric, nested rings of microphones . . . surrounding a central microphone." The Court also looked to examples of such a configuration in the figures that show "repeating or fractal-like configurations, such as concentric rings, ovals, or other shapes." Thus, the Court found that "the term self-similar informs skilled artisans, with reasonable certainty, about the scope of the invention."
ClearOne argued that "the written description's disclosure of fractals, concentric circles, and repeating patterns confuses, rather than clarifies, what arrangements are self-similar because those examples must be understood as distinct from self-similar configurations." The Court disagreed, finding that the terms "self-similar or fractal-like" and "self-similar or repeating" equate self-similar to fractal-like or repeating.
The Court also looked to a dictionary definition of self-similar as "the quality or state of having an appearance that is invariant upon being scaled larger or smaller" as well as a similar definition provided by ClearOne's own expert. ClearOne also attempted to convince the Court to focus separately on the terms "self" and "similar", as well as different possible interpretations of the term. But the Court noted that "[j]ust because a term is susceptible to more than one meaning does not render it indefinite," because "[s]uch a test would render nearly every claim term indefinite so long as a party could manufacture a plausible construction."
Accordingly, the Court affirmed the PTAB, and held that the amended claim was not indefinite.
While on its face this case might seem properly decided, there are a few considerations worth noting. The term "self-similar" is incredible broad. Famously, Benoit Mandelbrot, one or the pioneers of self-similarity, once wrote that even a straight line is self-similar. Further, the specification of the '493 patent never formally defines what it means by "self-similar", nor does it explain how the disclosed concentric geometric patterns of microphones exhibit the scale-invariance of the relied on dictionary definition and expert testimony. The specification does not define the arrangements mathematically -- or in any other particular fashion -- except with a few examples in the figures.
Ultimately, claims should provide a notice function and be able provide a reasonably certain answer to the question "Am I infringing or not?" It is not clear that this question has a precise answer with respect to Shure's claim.
This goes to show how high the bar can be to establish that even a broadly-defined claim term is indefinite. Further, this apparent breadth and lack of specificity in the claim language certainly opens up the claim to being vulnerable to more prior art that meets the eye -- notably, Mandelbrot's straight line.
ClearOne, Inc. v. Shure Acquisition Holdings, Inc. (Fed. Cir. 2022)
Panel: Chief Judge Moore and Circuit Judges Newman and Hughes
Opinion by Chief Judge Moore
