What cause EMI radiation?

I am confused with two EMI radiation causes on PCB:
1. changing current
2. impedance discontinuity

Assume AC signal on a 50ohm microstrip transmission line with 50ohm termination at the end, is there going to be any radiation?

Thanks

At different frequency, the impedance seen by the signal would differ, hence the transmission line model kicks in. In my view even with the impedance between device well taken care, I often see that device with high speed signals radiate.

A microstrip is a "leaking" transmission line and generally radiating to a certain extent. The effect is increased with a nonunity VWSR respectivly transmission line reflections and discontinuities in the geometry.

Radiated interferences are also caused by ground and power planes acting as antenna.

hi
These are two most important causes but not the all, I think everywhere we have current the potential vectors can exist and thus radiation will occur.