The U.S. Court of Appeals for the Federal Circuit recently reversed a district court’s construction of two means-plus-function claim elements because the construction improperly included not only the circuit, but also the signals that the circuit used to perform the claimed function. Northrop Grumman Corp. v. Intel Corp. et al., Case Nos. 02-1024,-1184 (Fed. Cir. Mar. 31, 2003).
The claims at issue recite a bus interface unit used in a computer network. The bus interface unit, as recited in the claims, included, in part, a "means for monitoring a plurality of logical signals" and a "means for defining the functional state of the bus interface units." In construing each of these elements as means-plus-function limitations, the district court first identified the function performed by each claim element and then identified the corresponding disclosed structure that performed that recited function. More particularly, the district court found that the "monitoring means" performed two functions: monitoring the logical signals that define the operational status of the bus interface unit and generating control signals that regulate a data transfer process. Then, focusing on a passage in the specification to discern the corresponding structure, the district court identified a sequence logic circuit that receives a set of signals to regulate the data transfer process between the bus and the memory port as the corresponding structure. Similarly, the district court included both a logic sequence circuit and a particular signal as the corresponding structure for the claimed "defining means."
The Federal Circuit reversed, finding that the district court improperly included signals in the corresponding structure for performing the "monitoring" and "defining" functions. The Federal Circuit reasoned that "the signals that are monitored by the ‘means for monitoring’ cannot be part of the structure that does the monitoring." Accordingly, the Federal Circuit held that the sequence logic circuit was the only structure that fell within the scope for "means for monitoring" and "means for defining."
Based upon the new claim construction, the Federal Circuit reversed the district court and remanded the case for an infringement determination.
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