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Optical counterpart of duckbill check valve in fluid dynamics

  1. Nov 24, 2016 #1
    In fluid dynamics there is a duckbill check valve to prevent the reverse flow.
    In EM wave an antenna emmits/receive at the same efficiency.
    Is there anyway one can make a check valve for antenna so that it emmits more than received or
    vice versa.......or perhaps emitts without even receive?
     
  2. jcsd
  3. Nov 24, 2016 #2
  4. Nov 24, 2016 #3

    Yes, that is one possibility, which requires an externally applied magnetic field.
    Is there any way that we can achieve the same purpose without external magnetic field?
    For instance, the material might change shape or rotate if it received EM wave in one direction hence cause the EM wave flow in the other direction impossible?
     
  5. Nov 26, 2016 #4

    Baluncore

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    There are many ways of making a non-reciprocal coupler.
    1. The microwave circulator; https://en.wikipedia.org/wiki/Circulator
    2. The TR switch used in a Radar; https://en.wikipedia.org/wiki/Duplexer
    3. The “180° Hybrid Coupler” “Ring”, “Ratrace”, or “Magic-T”.
    https://www.microwaves101.com/encyclopedias/hybrid-couplers
    Consider connecting the antenna to one terminal, then the RX and the TX to adjacent terminals λ/4 away on each side of the antenna terminal. The RX and TX will be unable to see each other but both will see the antenna.
     
  6. Nov 26, 2016 #5
    The third method (above) seems to be a special case for the first one?
     
  7. Nov 26, 2016 #6

    Baluncore

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    That may be true if you look at it from a purely analytic viewpoint, but you need to also consider the physical implementation and wavelength. Microwave circulators with waveguides, ferrite and magnets are not built for the HF band. The “Ratrace” can be built with long coaxial cables for operation on the HF bands. I am sorry about the duplication.
     
  8. Nov 26, 2016 #7
    For the circulator, what are the differences for 3, 4, 9, or perhaps 16 ports? Do they exits with different phase and hence different cancellation?
     
  9. Nov 26, 2016 #8

    Baluncore

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    Anything can be built if needed, but microwave engineers are conservative and so tend to use the the many three port circulators that are available as off-the-shelf components. The microwave circulator connected as an isolator is the closest equivalent to a “check valve”. Where a three terminal circulator is used as an isolator, two can be used in series to square the isolation ratio.

    Trees of hybrid transformers or transmission line transformers are assembled to make multi-port distributors and combiners. An arbitrary phase shift can be generated by using appropriate length transmission lines and transformers.
     
  10. Nov 27, 2016 #9

    Baluncore

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    The optical equivalent of a check valve would be an optical isolator; [/PLAIN] [Broken]
    https://en.wikipedia.org/wiki/Optical_isolator

    A partially reflective diagonal mirror can be seen as a combiner of two isolated inputs, that generates two outputs.
     
    Last edited by a moderator: May 8, 2017
  11. Nov 27, 2016 #10
    For the circulator, should the wave come from its side wall? Or, does not matter?
     
  12. Nov 28, 2016 #11

    Baluncore

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    I do not understand the question.
    What type of circulator? at what wavelength? what type of transmission line? which wave? Both walls are side walls, I guess it will depend on mode of propagation.

    An EM wave in a waveguide is guided by the conductivity of the walls. Current flows in the walls, but the EM wave fills the inside volume of the guide.
     
  13. Nov 29, 2016 #12
    By a circulator I mean
    https://en.wikipedia.org/wiki/Optical_circulator
     
  14. Dec 8, 2016 #13
  15. Dec 8, 2016 #14

    Baluncore

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    For microwaves, the waves are travelling between the walls of the waveguides. Since the EM transmission mode is important, the orientation of the ports need to be related. The perpendicular magnetic field requires the planar solution. The Magic-Tee is a four port coupler that requires perpendicular arms. [/PLAIN] [Broken]
    https://en.wikipedia.org/wiki/Magic_tee

    In optical-isolators the polarisation is also important, as the light passes through transparent materials with anisotropic properties that rotate the polarisation in a controlled way.

    Before you invent a spherical circulator you need to consider the perpendicular nature of the electric, magnetic and poynting vectors. You then need to apply the “Hairy Ball Theorem” to see why the ring structure and not the sphere is used; [/PLAIN] [Broken]
    https://en.wikipedia.org/wiki/Hairy_ball_theorem
     
    Last edited by a moderator: May 8, 2017
  16. Dec 8, 2016 #15
    So, in view of the hairy ball theorem, the conclusion is 3-D circulator is impossible?
     
  17. Dec 8, 2016 #16

    Baluncore

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    That depends on your definition of 3D. The hairy ball suggests a torus rather than a sphere.
     
  18. Dec 11, 2016 #17
    Is there any textbook explicitly calculate the irreversibility of a 3-port (or any port) circulator?
    or discussed similar devices?
     
  19. Dec 11, 2016 #18

    Baluncore

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    There are many advanced books available. Analysis of microwave junctions is often done using the multi-port “scattering matrix”, with frequency dependent parameters S11, S22, S12, S21, S31, etc.

    There is probably a beginners guide to circulator design in most general text books on microwave technology. You need a good technical engineering library.

    The publisher “Artech House” produces books in that field. Search their titles, then the web or local technical libraries.
    Do you have a big second hand bookshop in your city?

    There are second hand books available if you know what you want. Use; http://www.bookfinder.com/
    If you find what you want, try to support the Physics Forums website by buying through;
    https://www.physicsforums.com/threads/support-pf-buy-on-amazon-com-from-here.473931/
     
  20. Dec 11, 2016 #19
    Hey, just give me a reference like J. Kraus, Antenna, Chapter 5.
    You don't need to care whether is it advanced or not, nore do you need to care whether do I have a good technical engineering library...etc.
     
  21. Dec 11, 2016 #20

    Baluncore

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