Federal Circuit Affirms PTAB Obviousness of Zentian Speech-Recognition Patent Against Apple.

In Zentian Ltd. v. Apple Inc., No. 2024-2205 (Fed. Cir. Sep. 25, 2026), Judge Prost (joined by Judges Dyk and Mayer) issued a nonprecedential opinion. Zentian appealed from a Patent Trial and Appeal Board final written decision, issued June 11, 2024 in IPR2023-00035, holding all claims (claims 1-6) of U.S. Patent 10,062,377 unpatentable for obviousness; the appeal caption also lists IPR2023-01194. The '377 patent relates to speech-recognition systems.

The representative claim

As quoted in the Federal Circuit opinion, claim 1 of the '377 patent covers a speech recognition system comprising a first programmable device programmed to calculate a feature vector from a digital audio stream, where the feature vector comprises a plurality of extracted and/or derived quantities from that digital audio stream during a defined audio time frame; a second programmable device programmed to calculate distances indicating the similarity between a feature vector and a plurality of acoustic states of an acoustic model, with the feature vector received after calculation by the first device; a third programmable device programmed to identify spoken words in the digital audio stream using Hidden Markov Models and/or Neural Networks, using one or more distances calculated by the second device, including distances calculated from a first feature vector; and a search stage for using the calculated distances to identify words within a lexical tree comprising a model of words.

Board proceedings

Apple petitioned for inter partes review of all claims of the '377 patent. Apple relied on Jiang, U.S. Patent 6,374,219, and argued that Jiang disclosed encoding feature vectors into codewords using vector quantization. The Board construed "feature vector" to include not only quantities extracted from the digital audio stream but also derived quantities that are representations of the stream, such as the derived values of a codeword. On that construction, the Board found that Jiang disclosed the disputed limitation, claim element 1[g], and held all claims unpatentable as obvious.

Claim construction affirmed

Zentian's appeal centered on the construction of "feature vector." Zentian argued the term should be limited to "pure" feature vectors, meaning quantities actually extracted from the digital audio stream, and that Jiang's codewords were mere representations, not feature vectors. The Federal Circuit agreed with the Board. Claim 1 itself defines a feature vector as comprising "a plurality of extracted and/or derived quantities from said digital audio stream." Because different claim terms are presumed to have different meanings, "derived" means something different from "extracted," and the term is not limited to pure extracted quantities.

Zentian's Magritte analogy rejected

Zentian invoked René Magritte's painting The Treachery of Images ("This is not a pipe") to argue that representations of feature vectors are not feature vectors. The court was unpersuaded. Substantial evidence supported the Board's finding that vector-quantized codewords are representative of the digital audio stream and are feature vectors under the claim construction, and the court called the better analogy "choosing one pipe to represent a group of similar pipes," a phrase it took from Apple's brief. The court also rejected Zentian's argument that codewords determined in advance cannot be "derived from" a later audio stream: selecting the codeword that most closely resembles the quantities of a given audio stream means the codeword comprises quantities derived from that stream. It rejected Zentian's argument that the Board's construction dropped the requirement that the quantities be derived "from" the audio stream, and its argument that a codeword identified by a single-value index cannot comprise a plurality of quantities.

Disposition

The Federal Circuit affirmed the Board's determination that Jiang's codewords fall within the construed "feature vector" term and affirmed the Board's holding that all claims are unpatentable as obvious. The disposition is nonprecedential.

What it means

The opinion leaves the Board's unpatentability ruling on all six claims of the '377 patent in place. The court rested on claim 1's own words: because the claim reaches "derived" as well as "extracted" quantities, Jiang's vector-quantized codewords fall within "feature vector." The court added that the result would be the same whether the question is treated as claim construction or as a factual comparison to Jiang.

What to watch next

Zentian sued Apple over the '377 patent and four other patents in the Western District of Texas in February 2022. The case moved to the Northern District of California in June 2023 (No. 3:23-cv-02921) and was stayed in July 2023 pending Apple's inter partes reviews. The district docket shows status reports every few months, most recently on August 17, 2026, and no judgment. Zentian's complaint gave the '377 patent's expiration as September 2025. Watch for any rehearing petition in No. 2024-2205 and the next status report in the district case.