A coaxial DC Block is used when DC isolation is required to protect sensitive RF system components like receivers or test equipment. Richardson RFPD / Arrow RF & Power provides three (3) types of coaxial DC Block: Inner, Outer, and Inner/Outer.
Inner DC Blocks have a capacitor in-series with the center conductor (of the coaxial connection), which prevents the flow of direct current (DC) and minimizes the flow of audio frequency current, but provides only minimum impedance to RF signals (up to the rated maximum frequency in GHz). Similarly, Outer DC Blocks have the capacitor in-series with the outer conductor (of the coaxial connection). The Inner/Outer models have capacitors in-series with both inner and outer conductors.
Applications for DC Block include ground loop elimination, signal source modulation leakage suppression, system signal-to-noise ratio improvement, test setup isolation and other situations where undesired DC or audio current need to be prevented from flowing between different sections of an RF system.
Specific attributes which are important in selecting the right DC Block for your application include the coaxial Connector Type (N, SMA, BNC, etc.); Maximum Frequency (in GHz); the rated Voltage (V); and the Block Type (Inner, Outer, or Inner/Outer).