Digital Circuit Boards: Mach 1 GHz

4.20 Glossary

A/D Converter (Section 4.14): An integrated circuit that converts analog signal levels to digital signals.

Analog/Digital interface (Section 4.14): On circuits boards that contain analog and digital circuits, the interface occurs at the IC that handles both signal types. If the fields for the analog and digital signals use different volumes of space there will be no cross talk. This includes traces, components, connectors, and ground planes. Separate ground planes are never needed.

Coaxial (Section 4.5): A round outer cylindrical conductor geometry with a round center conductor. The outer conductor can be braid or a thin hollow metal tube. A coaxial cable is usually built to have a specific characteristic impedance. A low characteristic impedance requires that the conductor spacing be very small compared to the cable diameter.

Circuit board resonance (Section 4.6):

1. Circuit Sense.

The natural frequencies of the parallel capacitors used to decouple a circuit board. The series inductances of capacitors form resonant circuits that are all in parallel when the capacitors are paralleled. The resulting two-terminal impedance has a series of low and high values.

2. Digital Sense.

The back and forth movement of energy on an unterminated transmission line.

Decoupling transmission line (Section 4.4): A four-terminal capacitor where the electrical length of the transmission path is defined and the characteristic impedance at the load terminals is controlled in value. ...