rayspanRayspan has raised $12.5 million to further its technology for filtering out antenna interference so that cell phones can get better reception.

The second round in funding comes from Khosla Ventures and Sequoia Capital. To date, the company has raised $25 million. It’s a sizable round and it’s good to see money going into a company that’s built on science and technology research — a rarity in our web-focused venture world today.

San Diego-based Rayspan has been working on the technology since it was founded in April 2006. Its licensees began shipping their first products using Rayspan’s “metamaterial wireless technology” in 2007. To date, more than two million products have shipped with 10 million Rayspan-equipped antennae.

The new round of money will help the company expand its operations on a global basis, said Franz Birkner, chief executive of Rayspan.

The metamaterials can filter out two times to four times as much noise as the analog radio frequency components — known as filters, couplers, duplexers and other passive components. Birkner said the technology will likely prove useful in upcoming 4G cell phones, or those with a combination of high-quality voice and high-speed data communications. The metamaterials can also be used in wireless routers in home computer networks.

The idea of metamaterials was conceived in the 1960s, but it wasn’t until this decade that researchers made progress on it. Rayspan licensed patents from two of the leading researchers, David Smith at Duke University and Tatsuo Ito at the University of California at Los Angeles. The company has 47 employees. Full told, the company has 59 patent applications and granted patents.