Background
Sisvel International S.A. owns two patents directed to methods and apparatus for cell reselection signaling in cellular telecommunications networks — technology that governs how mobile devices hand off connections between cell towers. Sierra Wireless, Inc. challenged these patents in inter partes review (IPR) proceedings. When faced with PTAB’s invalidity analysis, Sisvel exercised its right as a patent owner to file a motion to amend its claims, seeking to substitute new claims in place of the challenged original claims.
Patent owners in IPR proceedings may propose substitute claims as a way to narrow their patents to avoid prior art while preserving some patent protection. However, substitute claims must meet several requirements, and one of the most fundamental is that they cannot be broader in scope than the original claims they replace. PTAB denied Sisvel’s motion to amend, finding that the proposed substitute independent claim was broader than the original in at least two limitations. Sisvel appealed, arguing that the proposed claims were overall narrower because other limitations had been added.
The Court’s Holding
The Federal Circuit affirmed. The court applied a strict rule: a substitute claim is impermissibly broader than the original claim if it is broader in any respect, even if other limitations in the proposed claim are narrower. The inquiry is not whether the proposed claim is broader on balance or in the aggregate — the comparison is limitation-by-limitation, and any broadening of any single limitation fails the test.
The dispute centered on two specific claim limitations. In the original claims, certain relationships between elements were described using the phrase “based on” — language that the court found required a direct causal or derivation relationship. The proposed substitute claims used the phrase “using” in place of “based on.” The court held that “using” is broader than “based on” because there are conceivable embodiments that would fall within “using” — meaning the element employs something — but would not fall within “based on” — meaning a result derives from or is caused by something. Because the substitute claim’s language could cover scenarios that the original language would not, the substitute claim was broader in this respect. The fact that Sisvel added other limitations to the proposed claim did not save it from the breadth problem.
Key Takeaways
- A substitute claim in an IPR motion to amend is impermissibly broader than the original if it is broader in any single limitation — net narrowing does not cure breadth in any individual element.
- Small word choice differences can determine whether proposed substitute claims are broader than original claims; “using” and “based on” have meaningfully different scopes for purposes of this analysis.
- Patent owners filing motions to amend in IPR must scrutinize each limitation of the proposed substitute claims against the corresponding original claim language to confirm that no limitation has been broadened, even inadvertently.
- A permissive specification statement (“the invention is applicable in any such system”) can support a broader claim construction, preventing patent owners from narrowly limiting claims through specification language that is framed as permissive rather than mandatory.
Why It Matters
Motions to amend in IPR proceedings have historically had a low success rate, and this decision illustrates one of the pitfalls that even experienced practitioners can encounter: inadvertently broadening a single element of a proposed substitute claim while adding other narrowing limitations. The no-broadening requirement is applied with strict, limitation-level scrutiny — there is no balancing test, and no amount of overall narrowing can fix a limitation that is broader in scope than what appeared in the original patent.
For patent owners defending patents in IPR proceedings, the practical implication is that motions to amend require careful side-by-side comparison of every word in every proposed substitute claim against the original claim language. This is especially true when changing prepositions, conjunctions, or transitional phrases that might seem stylistically equivalent but carry different legal scope implications. The decision also highlights the importance of specification language: when a patent’s specification contains permissive rather than mandatory language describing the invention’s scope, that permissiveness can weigh against constructions that would limit the claims — or, in the motion-to-amend context, support findings that proposed claim language is broader than the original.