DC blocking capacitor for RF receiver chips

Some RF receiver chips need an external DC blocking capcitor.

Could someone please advise the purpose of this?

And in what condition the DC signal might turn up ?
(e.g., test signal generated by equpiment might have DC ?)

Thanks for the help.

It's the other way round. The receiver chip has a DC on its input - terminating with 50 Ohm would corrupt the DC biasing.

A Dc blocking capacitor simply blocks any DC signal..... as the previous poster mentioned, connecting two stages with dissimilar DC bias points will screw up the biasing of both stages. So putting a simple capacitor solves the problem, at RF you need a relative good capacitor to ensure it does not affect the RF performance.
Maning that the series impedance presented by the cap must be much lower than the impedance of your circuit.