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Clarity in Patent Applications for Electronic Systems and Circuits

By Matthew Howell, Partner

Article 84 of the European Patent Convention requires that the claims of a patent application are clear and concise and are supported by the description. Failure to meet these requirements will result in an objection of lack of clarity.

When we looked at the decisions of the EPO’s Technical Boards of Appeal for applications in the “Basic Electronic Circuitry” International Patent Classification H03, we found 93 decisions that involved a question of clarity, compared to 100 decisions involving questions of novelty and 272 involving questions of inventive step. Clarity objections therefore seem to be less prevalent than novelty or inventive step objections in applications related to electronics, but they still occur quite frequently.

While many clarity objections can be overcome by simple claim amendments, there have been cases where avoidable clarity objections have been fatal to applications.

T552/16 is an example of a Technical Board of Appeal decision to refuse an application on the ground of lack of clarity. In this case the application related to a broadband power amplifier. Claim 1 defined a “Doherty amplifier” having a carrier amplifier and a peaking amplifier connected in parallel, each having a quarter-wave transformer connected to its output, as shown in Figure 1 below. This configuration resulted in there being no phase shift between the amplified signals output by the carrier amplifier and the peaking amplifier.

Figure 1: An amplifier as shown in the patent application


During examination of the application the Examining Division found a 1936 scientific paper by a Mr W H Doherty, the inventor of the Doherty amplifier, describing its principles of operation. The Examining Division considered that the power amplifier circuit claimed in the application did not meet the definition of a Doherty amplifier as it would be understood by the skilled person from the teaching of the 1936 paper. The Doherty amplifier described in the 1936 paper had a carrier amplifier with a first quarter-wave transformer connected to its output, but a peaking amplifier with a second quarter-wave transformer connected to its input, as shown in Figure 2 below. This configuration resulted in there being a 90 degree phase shift between the amplified signals. Thus the Examining Division found that the term “Doherty amplifier” implies a 90 degree phase shift between the respective outputs.

Figure 2: A Doherty amplifier as shown in the 1936 paper


During the appeal proceedings, the Board agreed with the Examining Division, arguing that the claimed invention was contrary to the principle of a Doherty amplifier as set out in the 1936 paper, which required a 90 degree phase shift. The Board held that the 1936 paper was a “perfectly suitable source of background art regarding Doherty amplifiers” and found that the document was “absolutely clear” about whether a Doherty amplifier requires the disputed 90 degree phase shift. Since the claimed amplifier did not generate such a phase shift, it could not be a Doherty amplifier and thus the claims lacked clarity and the application was refused.

T552/16 is perhaps an extreme example, but it does illustrate the importance of using clear terminology in the claims of a patent application.

Thus, when preparing a patent specification it is crucial that all of the terminology used to describe the invention is clear and would be understood by those operating in the relevant technical field.

In our experience, inventors and engineers often coin their own internal terms and expressions for circuit configurations in a particular project. Such terminology may be well understood by those working on the project, but it is not necessarily always the case that others will understand it. Thus, it is important that all of the terminology used in the patent specification is clearly understood by the inventors and their patent attorney.

If there is any doubt as to whether a term used by an inventor to describe their invention would be generally understood by those skilled in the art, it is sensible either:

  1. to avoid using it in the claims, in favour of more standard terminology, or
  2. to include in the description a clear definition of the term that could be imported into the claims in the event of a clarity objection.

Our Electronics Systems & Circuits team are always on hand to guide you through the pitfalls of patenting in this area. Feel free to reach out to us with any questions you might have.

This is for general information only and does not constitute legal advice. Should you require advice on this or any other topic then please contact or your usual Haseltine Lake Kempner advisor.

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