Announcement to be made today:

A start-up company ... says can expand the limits of a popular wireless Internet format, providing access to hundreds or even thousands of portable computer users at distances of more than 2,000 feet within buildings and about four miles outdoors.

The antenna uses the 802.11 technical standard, also known as Wi-Fi, which is currently limited to providing wireless Internet access to several dozen users within a few hundred feet of the transmitter. Wi-Fi is increasingly common in offices, airports, places like Starbucks shops and even in a growing number of households.

Executives for the start-up company, Vivato, based here, said they expected their technology to be especially suited to office buildings because it would enable so many more people to use a single Wi-Fi Internet connection simultaneously.

"We will change the way people think about the physics of Wi-Fi," said Ken Beba, the chairman and chief executive of Vivato, which is across from the Pac Bell Park baseball stadium.

The company does not plan to formally introduce its product or discuss pricing until the first quarter of next year. The announcement on Monday, instead, will be devoted to discussing the technology, which employs an antenna shaped like a large picture frame, about three feet by four feet and about three inches thick.

The Vivato technology, which stems from 1950's research for so-called phased-array antennas for military applications, makes it possible to electronically steer numerous radio beams from a single point. Focusing the beams increases their signal strength, and using large numbers of them greatly increases the antenna's traffic capacity.