One situation would be where a quarter wave line is between your circuit and the generator. The line is used for impeance transformation. The 0.5 dB of signal reflected from your circuit back to the generator is reflected at the generator end and has a second chance of getting into your cirucit.
Another similar case is with a half wave line. It can be any impedance and the source and load will "see" each other at their actual impedance.
One situation would be where a quarter wave line is between your circuit and the generator. The line is used for impeance transformation. The 0.5 dB of signal reflected from your circuit back to the generator is reflected at the generator end and has a second chance of getting into your cirucit.
Another similar case is with a half wave line. It can be any impedance and the source and load will "see" each other at their actual impedance.