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This is called phased array, and it's been around since WWII for radar applications: https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/P

This is called phased array, and it's been around since WWII for radar applications: https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/Phased_array More antennas can enable you to narrow lobes more - you may have not been phasing them properly to get that effect.

darkmighty 13y ago
Yea, and MIMO is should be not only beamforming (which, best case scenario, gives you one strong channel); but it uses multipath to create essentially two channels at the same frequency.
lutusp 13y ago
My sole reason for posting the example was to show how a small number of individual antennas could produce focusing lobes within a 2D space. Phased array radars use many more elements, much higher control over the wavefront, and for a different purpose. In a cellular antenna scenario, unlike phased array radar, you cannot avoid multiple lobes, but the advantage of phasing is still present. Adding antennas to the system (beyond three or four) becomes a case of diminishing returns. > More antennas can enable you to narrow lobes more - you may have not been phasing them properly to get that effect. There are paradoxical effects with more than a few antennas -- apart from the complexity issue. In some cases you will see lobes with strange shapes in locations having no benefit. With a circular array of antennas, you sometimes get concentric circles of high signal strength, not what you're after in the described system. Example: http://i.imgur.com/hK9BZnF.png http://i.imgur.com/hK9BZnF.png
- TTPrograms 13y ago
  I'd recommend you make your system scale appropriate. Considering that cellular transmissions are on the order of GHz, you're effectively simulating a circle of antennas around 1 m wide looking at what happens in the middle. That doesn't seem particularly relevant to the case of antennas being very far away (far-field vs near-field etc).
  - lutusp 13y ago
    Yes, understood. The diagram was only meant to show how interference works, not at all to represent the problem under discussion.

darkmighty 13y ago

Yea, and MIMO is should be not only beamforming (which, best case scenario, gives you one strong channel); but it uses multipath to create essentially two channels at the same frequency.

lutusp 13y ago

My sole reason for posting the example was to show how a small number of individual antennas could produce focusing lobes within a 2D space. Phased array radars use many more elements, much higher control over the wavefront, and for a different purpose. In a cellular antenna scenario, unlike phased array radar, you cannot avoid multiple lobes, but the advantage of phasing is still present. Adding antennas to the system (beyond three or four) becomes a case of diminishing returns. > More antennas can enable you to narrow lobes more - you may have not been phasing them properly to get that effect. There are paradoxical effects with more than a few antennas -- apart from the complexity issue. In some cases you will see lobes with strange shapes in locations having no benefit. With a circular array of antennas, you sometimes get concentric circles of high signal strength, not what you're after in the described system. Example: http://i.imgur.com/hK9BZnF.png http://i.imgur.com/hK9BZnF.png

TTPrograms 13y ago
I'd recommend you make your system scale appropriate. Considering that cellular transmissions are on the order of GHz, you're effectively simulating a circle of antennas around 1 m wide looking at what happens in the middle. That doesn't seem particularly relevant to the case of antennas being very far away (far-field vs near-field etc).
- lutusp 13y ago
  Yes, understood. The diagram was only meant to show how interference works, not at all to represent the problem under discussion.