As mobile handsets are expected to access more frequencies and networks, antenna technology has started grabbing more attention from manufacturers.
SkyCross came out with a new antenna scheme earlier this year called isolation mode antenna technology (iMAT) that the company says will allow multiple-in, multiple-out (MIMO) on a single antenna. WiMAX and Wi-Fi’s new 802.11n interfaces use MIMO, as do some advanced cellular technologies.
Another antenna company, Ethertronics, has embarked on a mission to talk carriers and handset OEMs into adopting an “active” antenna design for future handsets. Rick Segil, vice president and general manager of Ethertronics Americas division, says mobile devices soon will have to cover networks spanning a wide swath of spectrum, from 700 MHz all the way up to 2.1 GHz for cellular networks and even higher when you add in Bluetooth, Wi-Fi and WiMAX.
Segil says the laws of physics won’t allow a typical passive antenna to cover all those bands effectively. One answer, he says, might be to add more cell sites in a network but he argues that’s a lot more expensive than changing the handset antenna.
There are three technologies available that Segil says can help solve the problem. One is called “active matching,” by which the antenna actively selects the appropriate frequency. Another is physically changing the structure of the antenna to fit the frequency, something called “switched antennas.” The last is “null-steering,” which tunes the antenna to alter the receiving pattern so the antenna will not be affected by “null” spots in the signal patterns.
Segil says null-steering has the most potential benefit, with a 4 dB to 10 dB gain. Switched antennas provide a potential of 2 dB to 3 dB gain and active matching 1 dB to 3 dB gain.
These gains are going to take coordination with handset OEMs, chip manufacturers and antenna manufacturers. Ethertronics says the use of active antennas could drive up the cost of a handset by $2 to $5 but is well worth it in the coming age of multiple frequencies and multiple mode handsets.