I have often seen that in some high speed signals, for example, RGMII lines, which are supposed to have 50ohms single ended impedance between the signals and the ground, often have series termination resistors of small value, say, 10 ohms.
Whether this 10ohms is included in the single ended impedance measurement for the trace or not?
If so, would the trace impedance not be affected if I move to have higher resistor value?
Please tell me how to understand this?