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I am new here. Just had a question wondering if someone could answer.

Let's say I have a generator that can generate RF and send it through a cable (coaxial) if I attached the end of that wire to a flat aluminum plate of 4'x4' by 1/8" thickness.

Would the rf just propogate through all ends of the plate? Would there be energy around the plate? Would the coaxial cable itself have energy around it? Similar to how magnetic waves are created when electricity flows through a wire?

Thanks

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    \$\begingroup\$ It depends on the 1/4 wavelength mainly, otherwise it gets reflected \$\endgroup\$
    – D.A.S.
    Commented Apr 13, 2022 at 15:11
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    \$\begingroup\$ I wonder why you ask the question. Do you have a coaxial cable attached to a flat plate that you need to analyze? Or is it something you are considering building for some purpose? If so, what is the purpose? \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Apr 13, 2022 at 15:13
  • \$\begingroup\$ It also depends on the substrate Dk, if not air and the asymmetric feedpoint. \$\endgroup\$
    – D.A.S.
    Commented Apr 13, 2022 at 15:29
  • \$\begingroup\$ I am curious if any energy is generated when passing rf into a wire and possibly utilize that energy, or is it just a reverse since passing electrical current through a wire makes magnetic fields, would passing rf through a wire create electrical field? \$\endgroup\$
    – Longschool
    Commented Apr 13, 2022 at 15:33
  • \$\begingroup\$ @Longschool coax tries to keep all the fields inside the coax, that's the whole point and that's what makes it a good cable. However the plate at the end will probably radiate something. Again, what is the purpose of this question? Knowing the purpose should make it easier to solve your actual problem. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Apr 13, 2022 at 16:18

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The plate will act as an antenna. As an antenna, it will produce electric and magnetic fields around it. It will produce both far field radiation (fields that propagate away from the antenna indefinitely) and near fields (field patterns that are significant only relatively near the antenna and don't produce radiation away from the antenna).

It might be a good antenna or a bad antenna depending on various factors, such as the dimensions of the plate (relative to the wavelength of the signal), the location of the antenna relative to any nearby ground plane, the presence of nearby scattering objects, etc.

To determine whether it's a good antenna or a bad one, you have a couple of choices:

  1. Build it and measure.

  2. Use an electromagnetic simulator such as Ansys HFSS or Microwave Office to estimate the radiation pattern

  3. Use a look up table or empirical formula created by somebody who has previously studied antennas with similar geometry and produced these tools for estimating the properties.

Even if it is a good antenna, you likely will need to provide some kind of matching network (a small circuit connected between the feedline and the antenna proper) to optimize the coupling of energy from the feedline to the antenna.

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  • \$\begingroup\$ Thank you for your help. \$\endgroup\$
    – Longschool
    Commented Apr 13, 2022 at 18:03

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