The mathematical formula of relation between mutual coupling and the distance between

Hello everyone,

I whould like to know please the mathematical formula between mutual coupling and the distance between antennas?
And is there any relation between physical parameters of antenna (like width length, dielectic constant ,operating frequency...) and mutual coupling ?

Thanks a lot.

I think you are looking for this: https://en.wikipedia.org/wiki/Friis_...ssion_equation

To add to Volker's comment, I would say that using the Friis transmission equation assumes that the elements are in each other's far-fields, which may or may not be true in your case. In many cases, closely spaced antennas are in each other's near-fields, then the only good way to determine coupling is via 3D simulation.