In order to scale the linearity of a Variable Gain Amplifier, usually use the C/IM3 (the ratio of carrier power to 3rd intermodulation distortion) while the output is kept on 1Vpp (Peak-to-peak voltage) .
While measuring the harmonic distortion (also keep output 1Vpp), and assuming that amplifier gain is Av, we need an input signal with Peak-to-peak voltage 1Vpp/Av. To simulate or measure C/IM3, two tones with same amplitude X (also peak-to-peak), frequency f1 and f2, are needed. Should I use X=1Vpp/Av, or use X=1Vpp/2Av? The performance of C/IM3 of these two conditions differs about 12dB, which one is correct? thank you!!