Claims to “signal” with no reference to physical structure not patentable subject matterSeptember 20, 2007

In the first of two decisions today regarding the scope of statutory subject matter, the Federal Circuit held that claims directed toward a "signal" were not statutory subject matter under § 101. Earlier, the USPTO allowed claims directed toward a method of embedding data in a signal; the rejected claims were the reverse: they were the signals with the data embedded as opposed to a method for doing the embedding.

The court analyzed the claims in the context of the four categories enumerated in § 101. Because the Federal Circuit determined the claims were not directed toward a "process, machine, manufacture, or composition of matter," the USPTO's rejection of the claims was affirmed.

Judge Linn dissented, and approached the problem from the perspective of Diamond v. Chakrabarty, which generally characterizes "anything under the sun made by man" as patentable subject matter. The only things excluded from patentable subject matter in Judge Linn's reading of Chakrabarty are "laws of nature, physical phenomena, and abstract ideas." Because the "signals" claimed here are "made by man" and not "laws of nature, physical phenomena, [or] abstract ideas," Judge Linn would have found the claims drawn to statutory subject matter.

Nuijten invented a way to embed "watermarks," or hidden data, into signals in such a way that the amount of distortion in the signal is reduced. This technology is used, for example, to insert data into digital music and video to help protect the media against unauthorized copying. For example, Apple applies watermarks with data about the purchaser to music sold in its iTunes music store, with the goal being to possibly identify users who subsequently make unauthorized copies of those songs.

The USPTO allowed claims to a method of watermarking signals. The broadest allowed claim is claim 1:

A method of embedding supplemental data in a signal, comprising the steps of: encoding the signal in accordance with an encoding process which includes the step of feeding back the encoded signal to control the encoding; and modifying selected samples of the encoded signal to represent the supplemental data prior to the feedback of the encoded signal and including the modifying of at least one further sample of the encoded signal preceding the selected sample if the further sample modification is found to improve the quality of the encoding process.

Nuijten also sought claims to the signals themselves that had the watermarks embedded, in an effort to obtain patent coverage over signals using the technology regardless of the particular method employed. Claim 14 is exemplary:

A signal with embedded supplemental data, the signal being encoded in accordance with a given encoding process and selected samples of the signal representing the supplemental data, and at least one of the samples preceding the selected samples is different from the sample corresponding to the given encoding process.

The USPTO rejected these claims as drawn to nonstatutory subject matter, as the "signal" claimed had no physical attributes, instead just describing the "abstract characteristics of the signal and, thus, it [was] considered an 'abstract idea'" that is not patentable. Nuijten appealed this rejection.

The Federal Circuit affirmed. The court described the claims as directed toward "transitory electrical and electromagnetic signals propagating through some medium, such as wires, air, or a vacuum." Relying on the text of § 101, the court held that this did not fall into "any of the four enumerated statutory categories: 'process, machine, manufacture, or composition of matter.'" The court analyzed each category in turn.


The court noted that the claims do reference "the performance of acts." However, in the end, the claims were not directed toward the "ultimate product, not the underlying process," and thus, if anything, were product-by-process claims, not process claims. Accordingly, because "a process claim must cover an act or series of acts and Nuijten's signal claims do not, the claims are not directed toward a process."


As defined by the Supreme Court, a "machine" is "a concrete thing, consisting of parts, or of certain devices and combination of devices." Here, there are no "parts" or "devices," but instead only electrical signals. As stated by the court:

No part of the signal—the crests or troughs of the electromagnetic wave, or perhaps the particles that make it up (modern physics teaches that both features are present simultaneously) is a mechanical "device" or "part." A propagating electromagnetic signal is not a "machine" as that term is used in § 101.


This presented the trickiest question of the four. The court noted that the verb "manufacture" was defined in Chakrabarty to mean "the production of articles for use from raw or prepared materials by giving to these materials new forms, qualities, properties, or combinations, whether by hand-labor or by machinery." Based on this definition, the claimed signals are not "some tangible article or commodity," particularly when the signals are transmitted through a vacuum, which is devoid of matter. As a result, the signals themselves are not "manufactures."

Composition of matter

Nuijten did not contend that the claimed signals were "compositions of matter," which was defined in Chakrabarty as "all compositions of two or more substances and all composite articles, whether they be the results of chemical union, or of mechanical mixture, or whether they be gases, fluids, powders or solids.

Because the claimed signals did not fall into one of the enumerated statutory categories, the court held they were not patentable subject matter, and affirmed rejection of the claims.

Judge Linn dissented. Under his reading of Chakrabarty, "anything under the sun made by man" is patentable subject matter. The only exclusions from patentable subject matter are "laws of nature, physical phenomena, and abstract ideas." As stated by Judge Linn:

the most straightforward interpretation of the Supreme Court’s guidance in Chakrabarty is that an invention qualifies as patentable subject matter if it (1) is "made by man," and (2) does not involve an attempt to patent "laws of nature, physical phenomena, [or] abstract ideas."

The signals claimed here are both "made by man," and fall into none of those three exclusions from patentable subject matter. Accordingly, he would have reversed the rejection of the claims.

To read the full decision in In re Nuijten, click here.

← Return to Filewrapper

Stay in Touch

Receive the latest news and updates from us and our attorneys.

Sign Up