PHYSICAL DESIGN AND DEBUGGING
11.4.1.1.2 Strip Lines
A strip line is a strip conductor centered in a dielectric medium between two voltage planes. The characteristic impedance is given theoretically by the equation below:
ZO = (601 ve; In (5.98bhr (0.8 W + t)) ohms
where b = distance between the planes for controlled impedance as shown in Figure
The propagation. delay .is given by the following formula
tpd = 1.017 \l'Et.ns/ft
For
Typical values of the characteristic impedance and propagation delay of these types of lines are as follows:
ZO = 50 ohms
tpd = 2 ns/ft (or 6"Ins)
The three major effects of transmission line phenomenon are impedance mismatch, cou- pling and skew.
The follQwing section will discuss them briefly and provide solutions to minimize their effects.
Strip Line
+~---------Dielectric
Ground
Planes
