Activist investor Carl Icahn wants Motorola Mobility to “explore alternatives” for its patent portfolio just three weeks after Nortel sold off its intellectual property for $4.5 billion.

Motorola’s stock surged more than 12 percent on the news in Thursday afternoon trading on the New York Stock Exchange.

The handset maker, which has struggled to maintain its profitability, could reap billions from a spin-off of its patent portfolio, which includes more than 17,000 patents and 7,500 pending patent applications. By comparison, Nortel’s patent portfolio contained about 6,000 patents.

Motorola’s patent portfolio is “substantially larger” than Nortel’s and has “significant value,” Icahn said in an SEC filing yesterday.

“There may be multiple ways to realize such value given the current heightened  market  demand for intellectual property in the mobile telecommunications industry,” Icahn said, citing the size of Motorola intellectual property holdings and the company’s patents on 4G technologies.

In response to Icahn’s statement, Motorola said its board of directors and executives “continuously reviews the Company’s strategic direction and opportunities that it believes are in the best interests of the Company and all of its stockholders.”

Icahn led the charge to get Motorola to spin off its handset business, suing the company in 2008 in a move to gain seats on the company’s board of directors and force the company to split up. Motorola’s board agreed to split itself into two separately traded companies shortly after Icahn’s suit, though the separation wasn’t finalized until the beginning of this year.