Meaning
Low-impedance connections to a reference potential must be maintained even at frequencies where wire inductance dominates resistive effects. Implementing high frequency grounding prevents voltage gradients across a circuit board or metal enclosure, which would otherwise act as noise sources. This technique uses short, wide connections to minimize parasitic inductance.
Impedance Control
Parasitic inductance in thin ground wires creates high impedance at radio frequencies, rendering traditional wire grounds useless for noise suppression. A wire that acts as a short circuit at DC can become an open circuit or even an antenna at several hundred megahertz. For effective high-frequency return paths, engineers use wide copper foils or direct chassis connections.
This approach keeps the reference potential stable across the entire assembly.
Enclosure Shielding
Metallic shields require frequent, low-impedance contact points along their perimeter to prevent RF energy from leaking through gaps. If the spacing between contact points is too large, the gap behaves like a slot antenna and radiates noise. Utilizing conductive gaskets or closely spaced solder joints resolves this leakage risk.
Layout Execution
Multi-layer boards use a grid of ground vias to stitch top-side copper pours to internal planes. This stitching reduces the loop areas of return currents. Vias must be placed closely together to handle high-frequency signals.
