The ruling only establishes Rambus' liability and does not address financial remedies.
The FTC plans further hearings to determine appropriate damages for the "substantial competitive harm that Rambus' course of deceptive conduct has inflicted."
The FTC said Rambus deceived the technology industry by participating in the standards-setting process with the Joint Electron Device Engineering Council (JEDEC) without disclosing the company was developing patents that involved the specific technology ultimately approved by JEDEC.
JEDEC sought to avoid the incorporation of patented technologies in its standards. At a minimum, JEDEC hoped that any patented technology adopted would be available to be licensed on a royalty-free basis.
"We find that Rambus' course of conduct constituted deception under Section 5 of the FTC Act," the FTC ruling states. "Rambus' conduct was calculated to mislead JEDEC members by fostering the belief that Rambus neither had, nor was seeking, relevant patents that would be enforced against JEDEC-compliant products."
The FTC said JEDEC members acted "reasonably when they relied on Rambus' actions and omissions and adopted the SDRAM and DDR SDRAM standards."
Since the standards were adopted, DRAM chips have been used extensively in personal computers, printers, cameras and a host of other electronic products, and Rambus has sued competitors for patent infringement.
"Rambus withheld information that would have been highly material to the standards-setting process with the JEDEC," the ruling states.
"JEDEC expressly sought information about patents to enable its members to make informed decisions about which technologies to adopt."
"We are disappointed. We believe the ALJ guy got it right," Rambus lawyer John Danforth said in a teleconference early Wednesday morning. "It's extremely likely we'll be [appealing]."
The decision reverses a 2004 ruling by an FTC administrative law judge (ALJ) dismissing the antitrust charges.