Creating point in space with antennas - Page 1
Forum section: electronics / projects

author: bertoncelj
author_rank: Newbie
timestamp: August 21, 2015, 10:35:55 pm
content: This question is theoretical, using some antennas producing electromagnetic waves.Can you produce max waves, adding them, creating massive spikes like it showed in this video with water, but with multi antennas. Can you do this with electromagnetic wave in air with some complex mathematics, if you can, how can you measure it?Basically I am looking to create one unique point in space with electromagnetic waves. I imagine solving this problem with basic mathematics, if you put in space, couple of lines focus all of them in one point, you get one unique point in space which all lines intersect with each other. Now using same principle but with multi antennas. When they emit signal, in one point all electromagnetic signals will add up to maximum. In my mind this new maximum is similar, to this in water (video minute 2:50-3:10). Now, when you create max in one point, is it possible to capture this max point with receiver antenna, if you put antenna directly on this maximum (or very close to it). I am thinking same in water, if you swim directly on this spike wave that occur, you can fell it, but anywhere else you don't.I understand that beam forming exist (wi-fi modems), but there is huge space in one direction that have allot of max, for better signal. I just want one point maximum, that can be recognize with antenna which is directly on maximum.https://youtu.be/ewIr4lO4408?t=2m50s

author: unitedatoms
author_rank: Frequent Contributor
timestamp: August 21, 2015, 10:43:02 pm
content: There was old USSR experiment with using gigawatt lasers arrays to break the insulation in spot inside of vacuum. This would prove the existence of electron-positron pairs spontaneously existing for attoseconds any time in vacuum. My friend who worked in particle accelerators facility told me about it. I think the whole range of experiments was sort of secret, because the main purpose of lasers arrays was to ignite the beryllium capsules filled with deuterium so they had a positive energy output, like in tokamaks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 21, 2015, 10:49:30 pm
content: Yes, you can solve an inverse wave propagation scenario, and create a constructive interference pattern which does this. You need quite a lot of emitters, and each must be synchronous, phase matched, and phase controlled. Since EM waves travel through 3D space, you need a sphere (or other closed surface) of them around the target, which will require quite many antennas.It wouldn't be very practical: notice that, in the video, the water surface is absolutely perfectly smooth and flat, aside from the ripples being induced. There are no extra reflections, no obstacles for the waves to flow around (which would therefore require a much more complex solution to yield the same impressive spike). You might be able to concentrate waves around an antenna mounted on the end of a thin mast, but the same will be almost hopeless for an antenna joined to a computer chassis (and almost certainly so, over all the antennas, in any computer with diversity radio; my laptop for example has three antennas within).Were you just thinking of improving reception, or do you have much more esoteric or even nefarious things in mind?Tim

author: unitedatoms
author_rank: Frequent Contributor
timestamp: August 21, 2015, 10:53:49 pm
content: Not with arrays, but with mere phasing from single antenna and multiple reflections, one can tune the phase/frequency shifts to maximize the standing wave at the receiver's point. This is practical even for consumer's level stuff. This feature existed in GSM-900 base stations, when they could tune to Doppler shifts, reflections, by changing single cell base station antenna by receiving the report from handsets.Another application was adaptive optics. The flexible array of moveable mirrors are tuned to phase while using smallish tuning laser, then battle laser pulses to destroy the target.

author: SL4P
author_rank: Super Contributor
timestamp: August 22, 2015, 05:22:41 am
content: Arrr, you beat me to it.Standing waves. Think of a still body of water (e.g. a calm pond)Drop one or more pebbles in at different locations at the same or different times, and see where the direct and reflected waves intersect.Almost exactly what you are asking - and almost exactly the answer to the proposition.(Remember there are reflection effects from the depth of the pond as well - etc)