Interpreting Source/Load Stability Circles

Is this amplifier stable? This design is for 1.6GHz but I'm trying to determine If it's stable. How can you tell from the stability circles and S11 if it's stable or not? I read 'S11 should not intersect stability circles at corresponding frequency ranges' but I don't know how to interpret this. Does it mean that if S11 is inside a stability circle it's ok as long as the frequency of S11 is higher than the frequency of the stability circle?