BigBoss
In the showed plot, the inductor is the bonding.
usually this structure is used in advance of classical varactor tuning+ cap banks for VCO sub-bands.
Imagine you need to go to a fast production run and you have an high freq VCO (5 GHz).
With 1 nH inductor, just as an example, and a total switched cap bank of 1 pF, you got the correct freq.
How to deal with inaccuracy of bonding/unaccounted parasitics?
Adding such a module (for example 50 fF total), you can adjust in a couple of weeks (only last metal of a properly stopped process) 2.5% the VCO freq.
Don't tell YOUR Big Boss who gave you this hint... (joking of course).
Walkingsun, could you please attach the complete IEEE paper?
Mazz