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If we apply an AC signal to a capacitor, we can see only one type of charge on an individual plate. If we apply an AC signal to a patch antenna, there are two different charge distributions on the patch. The charge distribution also varies with the length of the patch.

enter image description here

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Antenna being used to transmit have a standing wave. The charge distribution will match that wave. This will happen regardless of antenna type (di-pole, patch, etc.)

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  • \$\begingroup\$ But how does charge distribution occur? How do electrons push each other to create two or more distributions over the patch? \$\endgroup\$
    – Mrunal Shinde
    Commented Jun 28, 2022 at 9:40
  • \$\begingroup\$ @MrunalShinde When an electric field (E-Field) is created on the antenna structure, then charges will move around based on the amplitudes in specific locations. Just like your pictures show. \$\endgroup\$
    – Aaron
    Commented Jun 28, 2022 at 14:14
  • \$\begingroup\$ But aren't the electric fields a result of charge distribution. I mean first the electrons should arrange themselves to create charge distributions then based on the two different charge separation electric fields are created. If there is no charge distribution how will the fields form? \$\endgroup\$
    – Mrunal Shinde
    Commented Jun 29, 2022 at 2:59
  • \$\begingroup\$ @MrunalShinde Ahh, the chicken and the egg question. Ask yourself, what is charge? Then ask yourself what is an antenna is made of? Do those things exist in equilibrium before an electric signal is fed to the antenna? What happens to charge in equilibrium when an external force is applied to it? \$\endgroup\$
    – Aaron
    Commented Jun 29, 2022 at 13:12
  • \$\begingroup\$ So basically the electric field from the source creates a charge gradient in the antenna. This gradient then pushes the electrons inside the antenna to rearrange themselves accordingly which results in charge distributions. The charge separation (as shown in above image) then creates an electric and magnetic field that is responsible for radiation. \$\endgroup\$
    – Mrunal Shinde
    Commented Jun 30, 2022 at 3:05

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