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To be able to take the maximum performance from a piece of equipment, every assembly transition must internally be adapted in moderation. This means, that the exit resistance Ra of the 1st assembly must like the resistance Re of the 2nd assembly.

assembly 1 assembly 2

Figure 1: Customization of two subsystems

Adaptation of two assemblies: The assemblies are drawn only as resistors connected in parallel.
assembly 1 assembly 2

Figure 1: Customization of two subsystems

With the help of extensive equations, the characteristic impedance is calculable.


ZL: characteristic impedance in Ω
L': Inductance in H/km
C': Capacitance in nF/km

The above formula holds for this in the simplified fall of zero-loss conduction with the conditions R' = 0 Ω/m and G' = 0 S/m.
For this condition, the characteristic impedance is frequency independent.

Why should the size of the capacitor C or the size of the inductivity L be frequency-dependent? At most, the impedance XC of the capacitor or the impedance XL of the inductivity is frequency-dependent. But these values are not asked for here!

This frequency independence you can see better if you analyze and convert the measurement units:

Only the units of measurement are considered in the formulas: So the root of (inductance by capacity) is the root of (Henry divided by Farad). Since Henry is equal to Weber per ampere and Farad is equal to Coulomb per volt, the equation can be transformed into the root of (Weber times volt divided by Coulomb times ampere). Now Weber is equal to one volt-second and Coulomb is equal to one ampere-second. This is inserted into the formula, the seconds can be shortened and the expression root remains (volt-square divided by ampere-square). So this is the root of ohm-square - so: Ohm.

It can be seen, that the measurement of impedances is the frequency independent unit Ω of a resistance.