Antenna impedance measurement without connecting it?

Hello,
is it possible to measure the impedance of an antenna without connecting the antenna by wire?

No, you can?t.
You can check somehow the resonant frequency of the antenna (using a coupled tuned circuit), but not the antenna complex impedance without a connection.

I suppose there is a theoretical, unpractical way since it is a two port network of sorts. You would have to terminate it in a short or open, then do sort of an impedance match between it and a reference antenna. This would mean submersing the two in a dielectric or some other media which you could vary the impedance and tune out the reactance to find the efficiency. You would have to know it's pattern, or else measure it from scattering.

Ideally your reference antenna would be an inverse-isotropic antenna, that is a sphere that radiates from it's inner surface towards the center. Place the DUT inside and fill it with with various media until it matches. Maybe you would not have to fill it with media if the sphere was small and the near fields coupled, then you could just tune a matching network on the reference antenna.

Thank you for the information.

@madengr: Do you have furhter information about your idea, e.g. a paper or so?

No, it was just a thought.

Ok