  Materials which possess a high local density of states varying at a
subwavelength scale theoretically permit to focus waves onto focal spots much
smaller than the free space wavelength. To do so metamaterials -manmade
composite media exhibiting properties not available in nature- are usually
considered. However this approach is limited to narrow bandwidths due to their
resonant nature. Here, we prove that it is possible to use a fractal resonator
alongside time reversal to focus microwaves onto $\lambda/15$ subwavelength
focal spots from the far field, on extremely wide bandwidths. We first
numerically prove that this approach can be realized using a multiple channel
time reversal mirror, that utilizes all the degrees of freedom offered by the
fractal resonator. Then we experimentally demonstrate that this approach can be
drastically simplified by coupling the fractal resonator to a complex medium,
here a cavity, that efficiently converts its spatial degrees of freedom into
temporal ones. This allows to achieve deep subwavelength focusing of microwaves
using a single channel time reversal. Our method can be generalized to other
systems coupling complex media and fractal resonators.
