Digital Circuit Boards: Mach 1 GHz

3.16 Glossary

Common mode (Section 3.5): Refers to an average interfering signal that appears between all conductors in a cable and the local ground. The term finds use in working with balanced signal lines. It is often the ground potential difference between two pieces of hardware. A common-mode signal is not always interference. There can be many common-mode signals present at the same time. In logic, common mode is called even mode.

Cross coupling (Sections 3.4 and 3.8): The unwanted coupling of signals between traces on a circuit board.

Culprit (Section 3.8): The signal causing coupling or interference.

Critical length (Section 3.12): Half the distance traveled by a wave in its rise time.

Dipole (Section 3.2): A conductor geometry used as an antenna. Two conductors in the shape of outstretched arms driven at the midpoint by a balanced signal.

Fall time (Section 3.4): The time for a step function to change from 80% to 20% of final value.

Far field (Section 3.4): The electromagnetic field far from a radiating source.

Forward coupling (Section 3.8 and 3.11): The cross coupling that moves in the same direction as the culprit wave. Forward coupling is a pulse that lasts as long as the culprit rise time. Forward coupling increases with time and is most severe on long lines.

Ground bounce (Section 3.14): The IR drop along the ground plane or on conductors between a ground pad and the die.

Induction field (Section 3.4): The field near a loop where the H field dominates; a low impedance ...