Phased Array Antenna is a highly interesting and facinating concept. There has been articles written about them such as the one last year in Scientific American magazine. In 2003, a few companies began launching Phased Array Antennas for WiFi.
Let me summarize this truly facinating concept of Phased Array Antenna techniques in a non-technical manner:
WHO USES THEM
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This type of antenna was more common for large bandwidth utilization in the cellular networks, ISPs and larger institution such as corporations, universities (for example: Indiana University of Pennsylvania) and of course the military. The military have been using phased array antennas for a while. It is only during the proliferation of cellular networks that we began to see their application in a more commercial and consumer oriented manner.
It's generally too expensive for the average home user. However, there are some facinating new products for WiFi.
THE STRUCTURE
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The structure is a multiple omni directional antennas lined up with equal distance from each other. A Signal Processor is than packed with the whole setup to do complex calculation of all the incoming and outgoing signals
It is also called the Smart Antenna because it can
Aim it's beam of signal and Adaptively point to their intended receipient. An Adaptive array can pinpoint the source of a radio signal and selectively Amplifying it. The result is double signal throughput and increased signal reach without using more power.
In theory, one could locate and pinpoint where the user is connected to the network such as WiFi. This is achieved by calculating the delay in the incoming signal reaching each antenna in the array. It is essentialy a super precise method of triangulation.
THE CORE CONCEPT
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[1] A normal dipole antenna (vertical metal rod) radiates signal in all direction, the further the weaker the signal. Normally for TV and Radio uses this version. [See 1st Picture]
[2] Now, Two-Antenna Array. Dipole A & dipole B placed at a distance between each other - half the wavelength, signal will reinforce each other at two ends while another two cancel each other out. That's how they get extra distance with the same power juxtaposition to the normal ones. [See 2nd Picture]
[3] Six-Antenna Array generates a beam that is narrower but extends further than Two-Antenna Array. However, facinating enough, it also generates smaller beams called signal LOBES. [See 3rd Picture]
[4] Each signal LOBES could be strengthen to extend outwards or focused at a specific user. This is Beam Switching, hence the name WiFi Switch. [See 4th Picture]
[5] With Digital Processor doing complex real-time calculation on an adaptive array of 12 antennas (eg.), each signal lobes (or beams) do not overlap others while allowing 2 users to use the same antenna
under the same frequency. How this was achieved is based on the idea that the array of antennas can tell which direction a signal comes from by calculating the reception delay between each antenna on the array, like how we workout where a sound is coming from with our ears. Then this is followed by using signal reinforcement and destruction to extend the lobes (or beams) to reach the user by varying the variables of each antenna on the array. [See last Picture]
For more information about Phased Array Antennas:
http://www.vivato.net/
http://www.navini.com/
http://www.personaltelco.net/index.cgi/PhasedArray
http://www.wi-fiplanet.com/columns/article.php/3314461
Phased Array Antennas
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