Popescul v. Brent: Federal Circuit Affirms Signal-Identification Patent Unpatentable
Inventors Alexandrin Popescul, Matt Colen, and Vladimir Ofitserov challenged the USPTO’s rejection of US15/394586 — a patent application covering systems and methods for identifying and characterizing signals in a data stream. The Federal Circuit affirmed the USPTO’s unpatentability determination after 580 days of appellate proceedings, leaving the application permanently rejected.
Inventors fail to overturn USPTO rejection at Federal Circuit
Inventors Alexandrin Popescul, Matt Colen, and Vladimir Ofitserov filed appeal No. 23-2119 with the United States Court of Appeals for the Federal Circuit on July 6, 2023, challenging the USPTO’s rejection of patent application US15/394586. The application, titled ‘Systems and Methods for Identifying and Characterizing Signals Contained in a Data Stream,’ covers signal-processing technology with potential applications across data analytics, communications, and AI-driven signal detection. The Acting Under Secretary of Commerce for Intellectual Property — at the time of closure, Derrick Brent — served as respondent on behalf of the USPTO.
The Federal Circuit issued its affirmance on February 5, 2025, upholding the USPTO’s finding that the claimed invention is unpatentable. An affirmance at this level means the appellate panel found no reversible legal error in the USPTO’s rejection — the agency’s patentability analysis, including any Section 101, 102, or 103 grounds, was deemed legally sound. For the inventors, the practical consequence is that US15/394586 will not issue as a patent through this avenue, and the subject matter as claimed remains in the public domain.
The 580-day duration from filing to closure is consistent with typical Federal Circuit timelines for contested patent prosecution appeals, though it slightly exceeds the median. The affirmance suggests the inventors faced significant legal obstacles — whether eligibility under § 101, prior art, or obviousness — that the panel found adequately addressed by the USPTO record below. What drove the specific patentability rejection and whether any dependent claims survived or were separately argued remains unclear from the public case record alone.
Filing to Unpatentable in 580 days
580 days — longer than the median Federal Circuit patent appeal (~14 months)
Federal Circuit affirms: what the unpatentability ruling means for both parties
Affirmance means the USPTO’s rejection survives intact
When the Federal Circuit affirms a USPTO decision on patentability, it signals the appellate panel found no reversible error in the agency’s legal reasoning or factual findings. The standard of review typically requires deference to factual determinations supported by substantial evidence, while legal conclusions — such as claim construction or § 101 eligibility — are reviewed de novo. Here, every ground of rejection argued before the Board and appealed to the Federal Circuit has been upheld.
No reversible error foundInventors exhaust appellate options; application will not issue
The affirmance effectively ends the inventors’ ability to obtain patent protection for US15/394586 as prosecuted. With the Federal Circuit having ruled against them, the remaining options are narrow: a petition for en banc rehearing, a petition to the Supreme Court for certiorari, or — if distinct claim language remains untried — a continuation application with materially different claims. The technology as claimed is now confirmed unpatentable, removing any enforcement rights the inventors might have sought.
Patent application rejected, finalUSPTO’s rejection sustained; unpatentability determination stands
For the USPTO as respondent, the affirmance vindicates the agency’s examination and PTAB-level reasoning. The Federal Circuit’s endorsement of the unpatentability determination reinforces the USPTO’s application of the relevant statutory grounds — whether § 101 subject-matter eligibility, prior art under § 102, or obviousness under § 103. This outcome strengthens the agency’s record consistency in evaluating signal-processing and data-stream characterization claims of this type.
USPTO rejection upheldSignal-processing space remains unencumbered by this application
Companies developing signal identification, data-stream analytics, or related AI-driven characterization tools face no patent enforcement risk from US15/394586. The affirmance confirms the claimed methods and systems are unpatentable as presented, leaving that technical space open. However, practitioners should note that the inventors may file continuation applications with amended claims — monitoring the application family remains prudent for product teams active in this domain.
FTO risk from this filing: lowFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Alexandrin Popescul | Individual | Inventors of US15/394586 — signal identification and data-stream characterization systemsSearch in Eureka ↗ |
| Co-Plaintiff | Matt Colen | Individual | Search in Eureka ↗ |
| Co-Plaintiff | Vladimir Ofitserov | Individual | Search in Eureka ↗ |
| Defendant | DERRICK BRENT, Acting Under Secretary of Commerce for Intellectual Property and Acting Director of the United States Patent and Trademark Office | Individual | Acting Director of the USPTO; respondent defending the agency’s unpatentability determinationSearch in Eureka ↗ |
| Plaintiff counsel | Anthony Sheh | Attorney | Counsel for Alexandrin PopesculSearch in Eureka ↗ |
| Plaintiff law firm | Williams & Connolly, LLP | Law Firm | Representing Alexandrin PopesculSearch in Eureka ↗ |
| Defendant counsel | Thomas W. Krause | Attorney | Counsel for DERRICK BRENT, Acting Under Secretary of Commerce for Intellectual Property and Acting Director of the United States Patent and Trademark OfficeSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The single-word verdict — AFFIRMED — is the Federal Circuit’s definitive endorsement of the USPTO’s unpatentability determination. At the appellate level, affirmance means the panel found no reversible legal error: factual findings by the PTAB or examiner are reviewed for substantial evidence, while legal conclusions receive de novo review. The basis of termination recorded as ‘Unpatentable’ confirms the rejection was sustained on its merits, not dismissed on procedural grounds. For the inventors, no further administrative remedy exists at this court level.
US15/394586 — Signal Identification and Data-Stream Characterization Systems
US15/394586, published as US20180189399A1, covers systems and methods for identifying and characterizing signals contained in a data stream. The application falls within the signal-processing and data analytics domain — technology relevant to communications infrastructure, cybersecurity signal detection, financial data analysis, and AI-driven pattern recognition. The publication date of the A1 document (2018) places the invention’s conception in a period of rapid growth in machine-learning-augmented signal processing, which may have sharpened the USPTO’s scrutiny of claim eligibility.
Strategically, this application targeted a broad and commercially valuable space: automated signal identification in streaming data environments touches virtually every industry reliant on real-time data processing. The Federal Circuit’s affirmance of unpatentability suggests the claims as drafted did not sufficiently distinguish the invention from prior art or abstract-idea doctrine. For competitors and R&D teams, this outcome confirms that the specific claim language of US15/394586 does not create an IP barrier — though the underlying technical concepts may still be protected by the inventors through differently scoped continuation claims or trade secret strategies.
Should your team run an FTO against US15/394586?
Product teams developing signal identification platforms, data-stream analytics engines, anomaly detection systems, or AI-driven pattern recognition tools should be aware of this application’s status. While the Federal Circuit’s affirmance of unpatentability means US15/394586 cannot be enforced as granted, the inventors retain continuation rights. Any company commercializing systems that identify or characterize signals in real-time data streams should monitor the application family for new prosecution activity that could yield an issued patent with adjusted claims.
PatSnap Eureka’s FTO Search Agent allows R&D and IP teams to map the full US15/394586 application family, identify any related continuation or divisional filings, and assess claim scope against your product architecture. Eureka’s real-time prosecution monitoring alerts you the moment new claims are published — so your FTO analysis stays current without manual docket tracking. Run a targeted FTO on the signal-processing landscape before your next product release milestone.
Run a freedom-to-operate analysis on US20180189399A1 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit appeals: signal processing and USPTO patentability rejections
Federal Circuit cases affirming USPTO unpatentability of signal-processing and data-stream characterization applications — relevant precedent for prosecution strategy and appeal risk assessment.
What this case signals for the signal-processing IP landscape
A Federal Circuit affirmance of USPTO unpatentability is rare to win on appeal — this outcome carries practical lessons for inventors and competitors alike.
USPTO rejections of signal-processing claims are hard to overturn on appeal
This affirmance is consistent with the Federal Circuit’s pattern of deferring to USPTO fact-finding under the substantial evidence standard. For inventors in data-stream and signal-characterization technology, it reinforces that poorly differentiated claims face a high bar at the appellate level — prosecution strategy and claim drafting at the application stage are critical.
FTO teams can deprioritize US15/394586 — but should watch the family
The Federal Circuit’s affirmance means the asserted claims pose no enforcement risk. However, the inventors retain the right to file continuation applications with amended claim language. Product and FTO teams developing signal identification or data analytics systems should monitor the application family for new filings that attempt to capture related subject matter through narrower or differently scoped claims.
Popescul v DERRICK — key questions answered
The Federal Circuit affirmed the USPTO’s unpatentability determination for patent application US15/394586 on February 5, 2025. The court found no reversible error in the agency’s rejection, meaning the application covering systems and methods for identifying and characterizing signals in a data stream will not issue as a patent.
The patent at issue is US application 15/394,586, published as US20180189399A1. It covers systems and methods for identifying and characterizing signals contained in a data stream — a signal-processing technology with applications in communications, data analytics, and AI-driven signal detection.
The public record identifies the basis of termination as ‘Unpatentable,’ confirming the merits-based rejection was upheld. The specific grounds — whether § 101 subject-matter eligibility, § 102 anticipation, or § 103 obviousness — are not detailed in the case metadata. The affirmance indicates the panel found the USPTO’s reasoning legally sound under the applicable standard of review.
The Federal Circuit’s affirmance forecloses further appeal of the claims as presented, but the inventors retain limited options: a petition for en banc rehearing, a Supreme Court certiorari petition, or a continuation application with materially amended claims. The technology as claimed in US15/394586 is confirmed unpatentable, but related inventions with differently scoped claims could still be pursued.
The affirmance of unpatentability means US15/394586 cannot be enforced against third parties, providing practical FTO clearance for the specific claimed subject matter. However, FTO teams should monitor the application family for continuation filings with amended claims, as the inventors retain the right to pursue related protection through new applications covering overlapping technical ground.
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