i have an input of
$$v_{in} = \sin{(2\pi\cdot f\cdot t)}$$
$$V_{out}=0.5+10\cdot V_{in} +0.1 \cdot V_{in}^3$$
SNDR is the ration between the power of the signal and the power of the noise . in the Vout we will have harmonics of f,3f,DC which of them i consider noise?
SNDR is the ration between the power of the signal and the power of the noise
No, it's the ratio of the signal to the noise-plus-distortion. A very similar term is SINAD i.e. total signal in noise and distortion and, it amounts to largely the same thing.
in the Vout we will have harmonics of f,3f,DC which of them i consider noise?
Well, none of them really. Noise is only really relevant if it's problematic and DC cannot really be regarded as problematic unless your signal is a DC signal. So your output, in the absence of any other information is: -
