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I What are the practical limits of constructive interference?

  1. Jun 19, 2017 #1
    The "wireless power" thread made me think of this, but I have pondered it before when it comes to microphone arrays etc
    You can easily find documentation on the interference patterns N in-line sources of waves generate. E.g.

    maxresdefault.jpg

    The annoying thing here is that you have infinitely extending lobes, which would be undesirable for something that tries to pinpoint delivery of (acoustic/EM) energy.
    It would seem to me that for example a source arrangement in a triangle would allow some spatially constrained Maxima inside it; but are there simple rules of thumb for this type of thing that constrain the patterns? I can imagine that with a complete ring of sources you could probably reverse engineer any pattern with a Fourier analysis, but that's also overkill on the other end.
     
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  3. Jun 19, 2017 #2

    anorlunda

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  4. Jun 19, 2017 #3

    sophiecentaur

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    This is a consequence of Diffraction. To direct energy in a specified direction with a certain required beam width you need an extended source. The narrower the required beam θ, the wider the necessary Aperture, d. (roughly θ = λ/2d) There are techniques for doing a bit better than the diffraction limit with 'Supergain Arrays' but there is not a lot of juice in that lemon. This is one of the reasons why Radiotelescopes are so enormous.
     
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