## Facts

- Translogic owned U.S. Patent No. 5,162,666, directed to a “Transmission Gate Series Multiplexer” used in digital logic circuit design.
- In related infringement litigation, Hitachi was an accused infringer and sought PTO reexamination of the patent.
- Hitachi filed multiple third-party reexamination requests; the PTO merged them into one proceeding.
- In reexamination, Translogic cancelled certain original claims, added new claims, and proceeded on a set of claims including claims 16, 17, 39–45, 47, and 48.
- The examiner rejected the claims as obvious under 35 U.S.C. § 103(a), relying on Gorai (or alternatively Tosser) in view of Weste, a standard VLSI design textbook that taught transmission gate multiplexers (TGMs).
- The Board of Patent Appeals and Interferences affirmed the examiner’s obviousness rejections and denied reconsideration.
- Translogic appealed the Board’s decision to the U.S. Court of Appeals for the Federal Circuit; Hitachi intervened.

## Issues

1. Whether the challenged claims were unpatentable as obvious under 35 U.S.C. § 103(a) over Gorai (or Tosser) combined with Weste.
2. How KSR’s direction against a rigid teaching-suggestion-motivation analysis affected the evaluation of motivation to combine in this reexamination appeal.
3. Whether substantial evidence supported the Board’s factual findings underlying its obviousness determination.

## Decision

- The Federal Circuit affirmed the Board’s decision sustaining the § 103(a) rejections.
- The court held the challenged claims unpatentable as obvious in view of Gorai (or Tosser) and Weste.
- Applying KSR, the court accepted that a person of ordinary skill would have had reason to use Weste’s textbook TGM implementations in the multiplexer stages described by Gorai/Tosser.
- The court concluded substantial evidence supported the Board’s findings on the scope and content of the prior art, the level of ordinary skill, and the rationale for combining references.

## Legal Principles

- A claim is unpatentable under 35 U.S.C. § 103(a) when differences between the claimed subject matter and the prior art would have been obvious to a person of ordinary skill at the time of invention.
- After KSR, a motivation to combine need not be shown only by explicit statements in the prior art; the analysis may rely on common sense, ordinary skill, and predictable uses of known elements consistent with their established functions.
- Standard technical textbooks can constitute prior art and can supply teachings and reasons to modify or combine other references.
- On appeal from the PTO, obviousness is a question of law reviewed de novo, while underlying factual findings (including motivation to combine and level of ordinary skill) are reviewed for substantial evidence.

## Conclusion

The Federal Circuit sustained the PTO’s reexamination rejections, holding the challenged multiplexer claims obvious under § 103(a) because a skilled artisan would predictably combine the multiplexer structures disclosed in Gorai or Tosser with the transmission gate multiplexer teachings in Weste under the flexible, post-KSR obviousness framework.


In re Translogic Tech., Inc., 504 F.3d 1249 (Fed. Cir. 2007)