bias tees tutorial
Problems is always the parasitic resonance of the inductor.
* Choosing a low value results in good performance at high freqs but mediocre performance at lower freqs
* Choosing a higher value inductance with a parasitic resonance in the band of interest is also not useful
* Combining many inductors is feasible but this very bad performance RF-wise due to the interaction of all parasitic resonances
You should investigate using the coilcraft conical inductor series. Really broadband up to 40 GHz and without parasitic resonance!
**broken link removed**