Listen
@CCatalyst first of all we just had some laugh , no worries everyone knows you simply made a typing error. And
@berkeman didn't put a "smiley" emoji under my last joke here (emphasis on a specific action very much added... :D) so even among us there is no 100% agreement about what we are really laughing about...
Let me try to help you out here,
@Baluncore is a sophisticated guy , he tends to give complex answers let me try to give a more simple one.
Your confusion about iron making B fields stronger is simple. Whenever you have some forms of current whether through a coil or even along a straight wire you have a B field set up.
Fields (including B) can travel through different mediums but there is a catch, different mediums attenuate (change/lessen) fields differently. It just so happens to be that for DC and low frequencies iron due to it's atomic structure can help "guide" a B field better than air.
So if one uses a core that is not air but metal one can have the same field strength with less effort, less current and/or turns. Sure other factors start playing a role like core material properties and the need for laminations in AC but that is another level of knowledge I suggest you read about.
Now talking about your Ghz frequencies which is way up there in the mm wave spectrum of microwaves there really aren't that many materials that can support a B field that changes so fast without introducing a lot of loss , energy wasted as heat in the core. + as
@Baluncore mentioned already there is a thing called skin effect so your effective core area will be just that of a thin layer on surface.
For this frequency range ferrites are used. Different ferrites are used for anything from Khz up to Mhz and some rare types even up to 20 and maybe even more Ghz. Or in other places no core at all is used, simply air, because air doesn't introduce any such losses as cores do at this high frequency, only drawback you need more current to have the same field strength.
Next you need to read about inductance, it's a "thing" that every conducting piece of wire has.
For a given frequency the more inductance the less "square wavy" your signal will be , at Ghz frequencies , even a few turns of wire could be the difference between a somewhat square like signal and a sine wave.
If you are ok with sine then no worries, because sine is probably everything you will get without some extra sophisticated hardware and implementation.
Now this being said yes you can phase shift one signal relative to another, because BOT (missing H, yes pun very much intended) are just signals and signals can be attenuated in different ways , they can be even overlapped and summed etc.