A backplane computer bus is a type of multilayer printed circuit board that has at least one (almost) solid layer of copper called the ground plane, and at least one layer of copper tracks that are used as wires for the signals. Each signal travels along a transmission line formed by its track and the narrow strip of ground plane directly beneath it. This structure is known in radio engineering as microstrip line.
Each signal travels from a transmitter to one or more receivers. Most computer buses use binary digital signals, which are sequences of pulses of fixed amplitude. In order to receive the correct data, the receiver must detect each pulse once, and only once. To ensure this, the designer must take the high-frequency characteristics of the microstrip into account.