RFC: Radio-Frequency Choke, it blocks the high frequency signals, but it acts as a short in DC and indeed it is used to feed the DC bias to an RF node.
RFC is component,
DC feed is requirement.
For a given RF circuit to power the DUT DC input is required. when you directly connect DC power by a simple transmission line say simple wire then RF performance will degrade.
DC feed is done by RFC.
Hope you understood now.