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How to get transmission for a particular mode?

    • sagar

      I want to collect transmission data for a particular mode. So I have used "mode monitor" and placed it perpendicular to Z-axis and in the same plane, my dipole source is placed. My goal is to collect the fundamental mode through the power monitors which are placed top and bottom of the waveguide perpendicular to the Z-axis and parallel plane to the "mode monitor". I have selected a particular mode in the "mode monitor" and selected the others monitors "2D-top" and "2D-bottom" for mode expansion for the mode of interest. (It is mentioned in the attached image)

    • sagar
      Thank you for the previous discussion. As you said in an earlier discussion Mode expanding monitor, As you said dipole can excite all the modes but the number of modes supported by the waveguide depends upon the V number and it depends upon the radius of the pillar. As I chose the radius in such a way that it only supports the fundamental HE11 mode so the propagation will happen corresponds to the fundamental mode only and it will be recorded by the power monitor placed on top of the pillar (Named as "2D_top").
      And in simulation, if I do the mode selection of fundamental mode through mode monitor and check T_forward (transmission into the selected modal field) of same power monitor placed top of the pillar should give the same value.
      May the dipole power is increasing for the environment but the transmission I am getting through the "2D_top" monitor is should correspond to the fundamental mode if the V number corresponds to the waveguide less than 2.405 or a value radius of pillar for a particular wavelength.
      Could you please refer to some articles to understand the parameters of mode monitors?
      Please let me know if I am missing something to take into account or if the placement of monitors is correct or not? Thank you.

    • Guilin Sun
      Ansys Employee
      Sorry, you are simulating different device from what you expect!
      mode is supposed to travel in an infinitely long waveguide so you can use FDE to get it.
      When the "waveguide" has limited length, it is a cavity! in a cavity you can only collect result outside of it, not inside, as inside it is the standing wave.
      T_total, T_forward and etc are listed in the table with explanations. I personally do not have additional information. Please let me know if you have any specific question, after reading all the replies here and in other posts.
      You may mix up the theories about the stable modes and the excitation of modes as well as cavity modes.
      Please take some time to think over what exactly you want to simulate: how do you apply a dipole in experiment? how do you know the top and bottom monitors only record the fundamental modes, where they locate in uniform background material, and mostly like in air? can the mode exist in the uniform material? what the definition of a mode?
      A little note:
      According to the screenshot, you are simulating a rod on a substrate, and place a dipole inside the rod. It is a cavity, and the dipole will excite all possible modes, including intermediate modes, radiation modes, and possibly non-propagation fields. However you expect it only excites the fundamental modes. and further, you want to use monitors in uniform material to capture the mode results, where the modes should be only inside the waveguide or cavity. You may compare them with theory in textbook, and please pay attention to the description of assumptions.

      Please read all the replies in other posts, rethink what you want to do and let me know if you have any specific questions. Please also note tat we will mainly support simulation/software questions as theories are so broad that we (I) may not have sufficient knowledge outside the normal knowledge. Maybe you are creating some thing very new.

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