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I have a linear horizontally polarized transmitting antenna and a dipole antenna, polarization mismatch losses can be approximated by 20log(cos(x)) where x is the misalignment angle.

What is happening inside the receiving antenna that causes the losses?

My explanation would be the following: the electric field component of the electromagnetic wave causes the free charges inside the receiving antenna to move across it's length (the length of the receiving antenna) inducing a voltage across it. The direction of the electric field is important here because as we misalign the antenna, the free charges move along a different path, with 90° being the worst case as the electrons only move across the diameter of the dipole.

Is this the correct way to think about it?

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Yes, that's pretty much it.

Furthermore, the H field (magnetic) induces current at right angles to the field lines, so this reinforces the idea that you want the antenna conductors perpendicular to the H field and parallel to the E field.

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  • \$\begingroup\$ @ Dave Thank you for that clarity on polarization. \$\endgroup\$ – analogsystemsrf Dec 12 '18 at 4:55
  • \$\begingroup\$ What about bent dipoles with different shape? Like this one: blog.atlasrfidstore.com/wp-content/uploads/2017/02/… How does horizontal polarisation work here? Wont the charges just bunch up at the first intersection? How will they flow if the force is only in 1 direction? \$\endgroup\$ – katrin sterner Dec 13 '18 at 14:49
  • \$\begingroup\$ @katrinsterner: No, nothing "bunches up" -- the charge carriers in the antenna still need to obey the physics of their local interaction. We're just talking about how the overall trend of their motion is influenced by the external fields. Such folded antennas are much less efficient overall, because much of that influence cancels out -- the only advantage that they retain is that they are electrically resonant at the frequency of interest. \$\endgroup\$ – Dave Tweed Dec 13 '18 at 14:56

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