It's called a "mixer", google that.
This isn't a simple thing, even though I wrote a simple word.
To really find your answer, and to get help here, you have to write alot more details on what you plan to do. Say about 200+ words worth of explanation.
The actual mechanism to shift a signal (say music or a phone call) to 5 ghz is to take the signal and turn it on and off with a set of diodes at a rate of 5 billion times pwer second. Your signal is now magically at 5 ghz, (sort of, some detail left- google "amplitude modulation" and see upper sideband and lower sideband info).
Higgler is right. We at least need to know the bandwidth of the signal and the allowed spurious level. It could be an easy design or a very difficult design, depending on your answer. For instance, if you have a 20 MHz wide signal somewhere in the 0 to 3 GHz region, and just want to upconvert it with to a higher frequency, you just mix it with the right tunable Local Oscillator.
