Federal Circuit rejects heightened standard for negative patent claims

The US Court of Appeals for the Federal Circuit declined to heighten the standard of eligibility for negative patent claim limitations, affirming a decision of the Patent Trial and Appeal Board (PTAB) to validate a patent covering the short-term storage of data in a computer program.

Judge Kathleen O’Malley dealt the blow to the patent challenger, semiconductor company Inphi, which had sought to revoke computer storage company Netlist’s US patent number 7,532,537. The patent is titled “Memory module with a circuit providing load isolation and memory domain translation”.

The asserted claim in the disputed patent covers a memory device that uses a double-data-rate chip which does not use a “column address strobe, row address strobe, or bank address signals”. Inphi argued that the negative claim limitation is not outlined in the patent specification and must be rejected.

O’Malley was joined by judges Jimmie Reyna and Edward Chen in issuing a unanimous opinion on Friday, November 13.

Initially, Inphi had success at the PTAB after the 537 patent was deemed obvious.  Netlist subsequently amended the patent to include the negative patent claim limitation.

Negative claim limitations are used by patent owners in the written application to distinguish the patent from existing prior art.

Inphi’s request for a hearing to challenge the negative claim was rejected by the PTAB in 2014. Inphi appealed to the federal circuit, arguing that the latest construction was impermissible under section 112 of the US Patent Code. It argued that such claims require “something more than properly describing alternative features”.

O’Malley disagreed. Citing the court’s 2012 decision in Santarus v Par Pharmaceutical, she said that the “patent-at-issue’s express recitation of (dis)advantages was sufficient to provide a reason to exclude the claim limitation at issue”.

In Santarus, the federal circuit ruled that negative claim limitations are acceptable if the patent specification “describes a reason to exclude the relevant information”.

O’Malley said: “The court did not hold, however, that such recitations were required to satisfy the written description requirements of section 112 for negative claim limitations. Nor do we see any reason to now articulate a new and heightened standard for negative claim limitations.”