Reflections at Boundaries

Lower Load Reflects a Negative Step

A load below the line impedance returns an inverted step. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A lower load gives a negative coefficient

The load is 2 ohms and the line is 4 ohms, so the coefficient is -1 over 3.

Γ=2 − 42+4=−13\Gamma={2\,-\,4\over 2+4}={-1\over 3}
Lower load reflectionThe negative coefficient is computed from the load mismatch.incidentreflectedline 4 ohmload 2 ohmGamma -1/3in 12 Vback -4 V

The reflected step changes sign

A coefficient of -1 over 3 sends a 12 volt step back as -4 volts.

V−=−13⋅12 V=−4 VV_{-}={-1\over 3}\cdot 12\ \text{V}=-4\ \text{V}
Negative reflected stepThe reflected label carries the sign of the mismatch.incidentreflectedline 4 ohmload 2 ohmGamma -1/3in 12 Vback -4 V