On October 19, 2023, the Court of Appeals for the Federal Circuit published a landmark decision on the issue of means-plus-function claims, especially for inventions that include processors/controllers and other software programmable devices.  WSOU Investments LLC v. Google LLC, Nos. 2022-1063, 2022-1065 (Fed. Cir. 2023).

Executive Summary

We strongly urge our clients to review and, if necessary, adapt their claim strategy and content of the specifications of their priority documents so the corresponding US patents are able to be successfully asserted in the US.  US patent applications based on Japanese, Chinese, or European priority documents are particularly at risk if those applications are (1) directly translated, (2) include “processor” in the claim, and (3) do not include some important supporting descriptions in the specification regarding how the circuitry and programmable devices are configured to perform specific operations.  This document includes some suggested language to include in priority documents that are yet to be filed so those documents can adequately support claim language to be used in the US application that avoids a means-plus-function construction.  We also strongly urge you to audit your pending applications to amend them when necessary to avoid means-plus-function.  If you wish, and as our service to you, we will help you assess your present situation so you can adapt your policies as needed.


In the United States patents, claim terms which are interpreted under 35 USC § 112(f) are limited to the structure disclosed in the specification and equivalents of that structure.  For claim elements interpreted under 35 USC § 112(f) that are based on software, the corresponding structure includes the algorithm disclosed in the specification.  Function Media, LLC v. Google, Inc., 708 F.3d 1310, 1318 (Fed. Cir. 2013) (“When dealing with a ‘special purpose computer-implemented means-plus-function limitation,’ we require the specification to disclose the algorithm for performing the function.”))  If there is not an algorithm disclosed in the specification for performing the function of the recited means-plus-function claim element, the scope of the claim cannot be determined and therefore the claim is indefinite.  Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1351-54 (Fed. Cir. 2015) (en banc).

Many of our clients include “processor configured to…” in the claims and assume this is not means plus function.  We often encourage our clients to use the language “circuitry configured to …{insert function}” because the MPEP cites case law that says “circuity” or “circuitry” combined with a specified function is sufficient structure to avoid invoking 35 USC § 112(f).  However, many of our foreign clients continue to directly translate their claims, and the translated English will be construed as means plus function by the USPTO and US courts.  This is a “silent problem” because it is permitted to have means plus function claim elements, but the legal protection of means plus function can be weak if not sufficiently supported by structures disclosed in the specification.

The Latest Federal Circuit Decision

In the WSOU Investment decision, the Federal Circuit held the “processor” in Claim 1 of U.S. Patent No. 8,965,045 to be a means-plus-function element under 35 USC § 112(f).  This claim is reproduced below.

  1. An apparatus comprising:

a viewfinder display configured to display a first and second picture;

a processor configured to move automatically a sub-set of pixels defining a target captured image that corresponds to the first picture, within a larger set of available pixels in a direction of an edge of the target captured image when a defined area of interest within the target captured image approaches the edge of the target captured image, ….

In view of the means-plus-function interpretation of the “processor” in the ‘045 patent, and because the patent owner did not explain to the court the corresponding structure including the algorithm, Claim 1 of the ‘045 patent was held to be invalid as indefinite.

Contrary to the interpretation of the “processor” in the ‘045 patent, the Federal Circuit held that the “processor” recited in Claims 1 of U.S. Patent No. 9,335,825 was not to be interpreted under 35 USC § 112(f):

  1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to at least:


Notice how in this claim, there is recited (1) a processor; (2) a memory which includes computer code; and (3) the combination of the processor, memory, and the computer code cause the recited functions to occur.

Practice Tips

35 USC § 112(f) continues to cause problems in U.S. patent applications, especially when the U.S. application claims foreign priority.  It is important that three factors be carefully considered when drafting applications that will be filed in the U.S. (or will serve as a priority document for a future U.S. application).

  1. The specification of the U.S. application and the foreign priority application should clearly describe and illustrate the hardware on which software is executed.
  2. The specification of the U.S. application and the foreign priority application should clearly describe and illustrate the algorithm or software which is used to achieve the claimed functionality.
  3. At least one set of claims should be written in a structural manner that will not invoke 35 USC § 112(f).


The specification should describe the specific hardware which can be used to achieve the claimed functionality.  Here is an example description of hardware which we recommend including in the U.S. application and any foreign patent application to which priority is claimed:

The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, ASICs (“Application Specific Integrated Circuits”), a CPU (a Central Processing Unit), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality.  Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein.  Processors may be a programmed processor which may execute programs stored in a memory. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality.  The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality.  When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.

For Japanese applications which will serve as priority applications for a future U.S. application, it is important that the priority document include a similar description of the hardware.  Below is Japanese language to be included in the Japanese priority application which corresponds to the above paragraph.

本明細書中に記載されている構成要素により実現される機能は、当該記載された機能を実現するようにプログラムされた、汎用プロセッサ、特定用途プロセッサ、集積回路、ASICs (Application Specific Integrated Circuits)、CPU (a Central Processing Unit)、従来型の回路、および/又はそれらの組合せを含む、circuitry又はprocessing circuitryにおいて実装されてもよい。プロセッサは、トランジスタやその他の回路を含む、 circuitry又はprocessing circuitryとみなされる。プロセッサは、メモリに格納されたプログラムを実行する、programmed processorであってもよい。




It is important that U.S. applications describe an algorithm which achieves the functionality of each claim element.  At an absolute minimum, each functional element appearing in the claims must be described using at least two method steps, and preferably more.  If only one step (and not a plurality of steps) is recited which achieve the claimed functionality, the courts may not consider such a disclosure to be sufficient. While not required, it is preferred that each of the method steps making up the algorithm be shown in the drawings in a flowchart.

Claim Language

Based on the WSOU Investment decision, the term processor may (or may not) be considered a means-plus-function element under 35 USC §112(f), depending on how the specification and claim are written.  If the claim is to recite a processor, the claim should be written in a similar manner as the Federal Circuity found to be structural (and not means-plus-function) in the WSOU Investment decision.  That is, a Federal Circuit approved claim format is:

  1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to at least:


As another format to consider, and as explained in MPEP 2181, the Federal Circuit (Mass. Inst. of Tech., 462 F.3d at 1355-1356, 80 USPQ2d at 13) has previously indicated that the term circuit or circuitry, combined with a description of the function of the circuit or circuitry, connoted sufficient structure to one of ordinary skill in the art.  Circuitry can be one or more circuits, and therefore may be desirable for multi-processor systems, cloud computing, etc.  Therefore, another claim format approved by the Federal Circuit, and reflected in MPEP 2181 is:

  1. An apparatus, comprising:

circuitry configured to

{insert function}

US case law changes, and so there is not an absolute guarantee that there will not be a case in the future in which circuitry is considered to invoke 35 USC § 112(f), but under today’s U.S. law, circuitry along with a proper definition of circuitry in the specification, should not invoke an interpretation under 35 USC § 112(f).


The WSOU Investment decision demonstrates the continued importance of properly drafting patent applications to take into consideration the pitfalls of 35 USC § 112(f).  Companies that do not draft their applications and claims to take into consideration 35 USC § 112(f) could find out the hard way how unforgiving claims which have a means-plus-function interpretation can be.