What is Line
Line refers to a transmission line used for carrying electrical signals between components on a printed circuit board. A transmission line consists of two copper traces: a signal trace and a return path (ground plane), with the thickness between the two traces made up of the PCB dielectric material. These transmission lines are crucial for ensuring the successful transmission of signals from their transmitters to their receivers.
In a PCB system, all input/output (I/O) signals travel through transmission lines. For single-ended I/O interfaces, both the signal trace and the reference plane are necessary to transmit a signal from one place to another on the PCB. On the other hand, for differential I/O interfaces, the transmission line is formed by the combination of two traces and a reference plane.
The length of the transmission line plays a significant role in its design. Short lines do not require special considerations but for lines longer than a certain critical length, transmission line effects must be taken into account. This involves designing the lines as controlled impedance lines to ensure proper signal transmission.