Magnetics for transformers for over 200 MHz

I would like to know who produces magnetics for frequencies over 200 MHz. I have heard even about ferite for 4 GHz. How can I get information on permeability and tan(delta)?

Look at a hybrid splitter/combiner magnetics. This is a 50 Ohm 1:1 power splitter/ combiner with coil orientation to offer isolation when balanced.
These are also called DC3's.. With higher turns ratios, we get DC6, DC12, DC20, DC32 etc.

TDK will have data now shared with partner companies. http://www.digikey.ca/Web%20Export/S...f?redirected=1
But due to non-linearities, generally used for noise suppression not energy storage or conversion.

Usually air coil or printed coil transformers are better for controlled impedances for power coupling transformers or coaxial resonators.