A federal judge dealt a setback Tuesday to Qualcomm Inc.’s defense against an antitrust lawsuit brought by the Federal Trade Commission, ruling that the chip maker must license some of its industry-essential patents to rival chip suppliers.

The ruling Tuesday by U.S. District Judge Lucy Koh in San Jose, Calif., poses a threat to the Qualcomm’s business model, analysts said. Its technology is widely used in smartphones, but the San Diego-based company hasn’t licensed patents for that technology to chip-making rivals like Intel Corp. Instead, it has included licenses only for manufacturers or device makers, charging a percentage of the price of a smartphone.

When Qualcomm’s intellectual property was incorporated into cellular communications standards, the company made commitments to standard-setting organizations that it would make its relevant patents available for use. Qualcomm has argued that the agreements didn’t require it to license technology to rivals.

Judge Koh rejected that argument. She said court precedent established that Qualcomm’s commitments “include an obligation to license to all comers, including competing modem chip suppliers.” And those licenses have to be offered on fair and reasonable terms, the judge said.

“This is a game-changer for the industry,” said Florian Mueller, an intellectual-property analyst who studies patent litigation.