IP3 circle help

Hi friends,
Anyone has heard of IP3 circle?I heard of noise circle,power circle and so on,but i never heard IP3 circle,aneone chan share me documents about this topic?
Thanks

It is one of the main parameter in this fast growing communication requirements with multi-carrier yet linear amplifier design.
The word circles will not applicable near saturation power levels they are called contours as their radius can not hold good

Go through the link for more details
http://home.sandiego.edu/~ekim/e194r..._stability.pdf

Thanks kspalla.you are always kind.