Shares of Santa Barbara-based semiconductor firm Resonant, which has a key development deal with a major supplier to Apple, were up 50 percent in the first day after it raised $16.2 million in an initial public offering.

The company began trading on the Nasdaq under the symbol RESN after selling 2.7 million shares at $6 a share. By midday May 29, Resonant’s first day of trading, shares had hit $9. The deal netted Resonant $14.8 million after fees to underwriter MDB Capital Group.

Resonant has a new design for a mobile phone component called a duplexer, and its IPO builds on a $7 million private placement that it raised last summer. The company is a spinout of Superconductor Technologies, a firm that was working on materials to transmit electricity more efficiently before it moved its headquarters to Austin, Texas, in 2012.

Resonant is a development-stage company and has not built a commercially viable device with its design. However, it is has a development agreement with Skyworks, which supplies components for the Apple iPhone and many other mobile devices, and plans to have a production-ready device by the end of this year.

“Skyworks has an option to license our duplexer design at already agreed-upon royalty rates upon completion. We will own our duplexer design and all related intellectual property,” Resonant said in securities filings.

Resonant’s duplexer sits between the analog antenna and digital parts of a mobile phone and selects which frequencies to use for sending and receiving signals. Current duplexers can handle only a set number of frequency bands at a time, which has caused them to take up more space and cost more in newer bandwidth-hungry designs.

Resonant’s device can be tuned to handle different bands, lowering costs and saving space, the company said, though its first efforts will be a single-band design.

But it is the development agreement with Skyworks, which has an outpost in Thousand Oaks, that is likely driving investor interest. In the duplexer market, Skyworks has a global market share of 40 to 45 percent, Craig Ellis, co-director of research with B. Riley & Co., told the Business Times earlier this year.

“Skyworks is the biggest player in their marketplace,” Ellis said. “Their use of a technology would have the potential to be big.”

Superconductor Technologies retains an 18.5 percent stake in the company. Lone Wolf Holdings, a New York-based fund headed by Peter Appel, owns 24.1 percent of the firm.