The doctrine of claim differentiation is at its strongest where the limitation that is sought to be “read into” an independent claim already appears in a dependent claim and is the only meaningful difference between the claims. The failure of an inventor to disclose an alternative embodiment in the patent specification, despite having contemplated it, does not justify excluding that embodiment from the coverage of the claims.

On appeal from the International Trade Commission (ITC), the Federal Circuit reversed the ITC’s finding of noninfringement based on errors construing critical claim terms in the patents-at-issue.

The technology that the patents-at-issue are directed to is the transmission of unique codes from a cellphone to a cellular base station to establish a communication link that transmits the telephonic message. At issue were the administrative law judge’s construction of the following claim terms (1) “code” was limited to a “spreading code” which is used to increase the bandwidth of another signal; and (2) “increased power level” required that “the power level of the code signal [continuously] increases during transmission.” The court found that the ITC erred in not according these claim terms their ordinary meaning.

The court held that the “code” claim term is not limited to a “spreading code” because neither the specification nor the prosecution history provided a restrictive definition of the claim term. Furthermore, according to the court, the doctrine of claim differentiation provides a powerful argument against construing the term code restrictively because the restriction of a “spreading code” is recited in a dependent claim. The Federal Circuit found this to be an “especially strong” argument because there would be no meaningful difference between the independent and dependent claims if “spreading code” were read into the independent claim. The court found the ITC erred in relying on the fact that the specification identified only spreading codes. Further, the ITC erred because its definition of “spreading code” differed from the expert witnesses and would exclude preferred embodiments in the specification from falling within the scope of the claims. Such a result is rarely, if ever, the correct construction.

The court held that the “increased power level” term was not limited to embodiments featuring continuous increases in power during the transmission process. Rather, the term also includes embodiments, such as the accused infringing device, that employ discrete power increases that occur between individual transmissions. The court found that the plain meaning of the term is not limiting to continuous increases of power. The court also found that while the embodiments of the patent involve continuous increases of power, there is no indication that the patentee intended to limit the claimed invention to disclosed embodiments. Finally, the ITC pointed to conception documents showing sketches of the two types of transmissions, continuous and stepwise, as evidence that the inventors only intended to cover continuous transmissions by only disclosing those embodiments in the patents. The court rejected the argument, finding that “the inventors’ failure to include a reference to the alternative embodiment in the specification does not justify excluding that embodiment from the coverage of the claims.”

A copy of the opinion can be found here.