radio frequency choke


A radio frequency choke (RFC) is a circuit element designed to present a high impedance to radio frequency energy while offering minimal resistance to direct current. RFCs are frequently used in series with power supply leads both to keep RF from coupling via undesired power supply paths and to prevent power supply components from paralleling undesired impedances across the RF circuit.
When selecting an RF choke, the first inclination might be to pick one with the highest inductance available. This is often a poor strategy, since the nonideal behavior of RFCs means that they will have both shunt and series capacitances, causing self resonances at a variety of frequencies. This self resonant behavior can actually cause an RFC to behave like a coupling capacitor at some frequencies ! It’s better to select a choke which presents an impedance several times that of the RF circuit at the point of connection and presents broadband high impedance behavior in the frequency band of interest.