In Technology Properties Limited LLC v. Huawei Technologies Co., Ltd., Appeal Nos. 2016-1306, -1307, -1309, -1310, -1311, the Federal Circuit vacated a portion of a district court’s claim construction because the district court erred in applying prosecution disclaimer to limit the scope of the claims.

The district court construed a claim limitation for an “oscillator.” The claim was narrowly construed based on statements made by the patentee during prosecution to overcome two prior art references, Magar and Sheets. The term “oscillator” was construed to have a “frequency [that] is not fixed” based on prosecution statements that distinguished Magar, and was construed to “not require a control signal” based on prosecution statements that distinguished Sheets. In light of the narrow construction, the parties stipulated to non-infringement, and the patentee appealed.

The Federal Circuit agreed with the district court’s Magar-based application of prosecution disclaimer. The patentee made clear and unmistakable statements throughout the prosecution history that the claimed oscillator was distinguishable over Magar’s fixed-frequency oscillator. Therefore, the Federal Circuit affirmed the district court’s narrow construction of “oscillator” as having a frequency that is not fixed. The Federal Circuit noted the patentee likely disclaimed more than was necessary to overcome the examiner’s rejection, but explained that the scope of what is surrendered by prosecution disclaimer is not limited to what is absolutely necessary to avoid a prior art reference.

However, the Federal Circuit disagreed with the district court’s Sheets-based application of prosecution disclaimer. The patentee made statements that the claimed oscillator was distinguishable over Sheets’ particular use of a control signal. But these statements did not extend to any use of a control signal. Therefore, the district court erred by holding that the patentee disclaimed any use of a control signal, and the Federal Circuit vacated the district court’s claim construction and remanded the case.