The yellow circle represents the amplifier limiting level.
The blue vector represents a signal vector in limiting, rotating at angular frequency, ω_s.
The red vector represents the equivalent input noise, scaled back to the limited signal, rotating at angular frequency, ω_n.
The green vectors represent the output contra-rotating noise vectors following limiting, one at angular frequency, ω_n, the other at angular frequency, (2ω_s-ω_n).
The magenta vector represents the summation of the output noise vectors showing complete compression of in-phase noise but unattenuated quadrature noise.

User Notes:
Note the output noise vectors are half the amplitude of the input noise vector, and that the corotating component is in-phase with the input noise vector.