Carl Icahn increased his position in Motorola Inc. in a likely sign of confidence in the telecommunications-equipment vendor.

Icahn, through his various funds, increased his stake in Motorola to 203.3 million shares, or 8.75% of the company's total outstanding shares, according to a recent filing with the Securities and Exchange Commission. At the end of last year, he owned 119.8 million shares, meaning he almost doubled his shares.

Icahn's additional investment may follow the belief on Wall Street that Motorola is on the rise. The company reported improved smartphone sales in the first quarter, helped largely by Verizon Wireless's aggressive push of the Droid. Co-Chief Executive Sanjay Jha reiterated his belief that the high-profile mobile-devices unit will return to profitability by the end of the year, while the rest of the company's units continue to post a profit.

Shares are up more than 13% since the end of January. They recently were at $6.86, up 3.9% on the day.

Icahn has played an influential role in Motorola's direction over the last three years. In 2007, Icahn took a large position in the company and attempted to win a board seat. Continued losses and slumping sales due to the lack of a worthy follow-up to its blockbuster Razr cellphone fueled increasing criticism from shareholders.

Motorola headed off a proxy battle with the investor by agreeing to take two recommended directors on the board. In the midst of the fight with Icahn, former CEO Ed Zander resigned from the company, and Motorola decided to spin-off its mobile devices unit.

Two years later, Motorola is preparing the company for a split, which is slated to happen in the first quarter of 2011. Jha will run the mobile-devices business, as well as the cash-generating set-top box unit. Co-CEO Greg Brown will run the networks and enterprise-mobility divisions.

In a recent interview with Dow Jones Newswires and Wall Street Journal editors, Brown said that he believed that the split remained the best move for the company, noting that it would unlock more shareholder value than if the pieces stayed together.