Bluetooth and Wi-Fi share frequencies in the 2.4 GHz ISM band, causing signal degradation when both are enabled in the same device. That's no longer an issue, thanks to antenna systems based on nanotechnology.
Oddly enough, this article came about because of a repair call. I received a voice mail from a friend, his Wi-Fi wasn't working. After initial checking, it appeared the Atheros AR9000 series 802.11n/Bluetooth combo mini card was to blame. Still, I wanted to check the antennas and feed cables. To my surprise, there was only one antenna.
My friend wasn't the least bit interested in this new discovery, just wanting his netbook back in working order. On a hunch, I reseated the board. That's all it took. On my way home, I started wondering about something. What happens if both Bluetooth and Wi-Fi are enabled and transmitting at the same time?Previous article may explain
For reasons unknown, I remembered an article I wrote two years ago: iMAT: MIMO without multiple antennas. The post was about how metamaterials are used to create antenna systems that overcome something called coupled interference. To understand what that means, let's review MIMO.MIMO causes coupling
MIMO technology requires multiple transceivers, each with their own antennas. That need invites unwanted signal coupling, because the small package size does not allow sufficient physical separation of the antennas. It's likely a significant portion of one transceiver's output is being absorbed by one of the other transceiver/antenna systems built into the Wi-Fi device.The solution
Since it's not practical to make Wi-Fi devices larger, another solution is needed. Enter SkyCross, a global designer of high-performance antenna solutions. SkyCross came up with iMAT (isolated Mode Antenna Technology). This technology mates a single antenna to multiple transceivers, abating the coupling phenomena. The following illustration (courtesy of SkyCross) depicts one configuration:
The next SkyCross graph displays how using a single antenna with multiple feeds has less coupling than multiple antennas:
Reducing coupling is important, by allowing more power to be radiated where it's needed. For more details, the SkyCross paper, "Isolated Mode Antenna Technology," is a good place to start. Last week, I wrote about Beceem Communications and how their new chip set will seamlessly transfer between WiMAX and LTE, I wonder if that would be a good fit for iMAT. Possibly, but more to the point, SkyCross has created iMAT systems to solve another thorny problem.Next accomplishment
Remember my friend's netbook and my pondering about Bluetooth and Wi-Fi working together. I am not sure if it's curiosity or what, but I wanted to find out how that worked. It didn't take long. SkyCross once again provided the answer.iMAT keeps them separate
There is a news release on the SkyCross Web site explaining how their researchers used iMAT's features to create a solution, whereby Bluetooth and Wi-Fi coexist. I'll let them explain:
"In this instance, iMAT enables a single antenna to have one feed dedicated to Wi-Fi and another feed shared with Bluetooth, which uses the chip set providers' time-sharing and adaptive frequency hopping algorithms. The very high, built-in isolation between the two feeds enables both to operate at the same time in a very small space."
The following diagram (courtesy of SkyCross) shows how iMAT differs from the conventional approach.
What's not to like. iMat decreases the number of required antennas from three to one. That reduces cost and saves valuable space. It also eliminates the coupling interference problem associated with multiple antennas in close proximity.Final thoughts
I read about nanotechnology all the time. Yet, its potential never ceases to amaze me — from the possibility of creating an electromagnetic cloak to what SkyCross has been able to accomplish. I'm glad I was more curious than my friend.
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