image rejection calculation

For example, give the calculator the amplitude mismatch 0.2dB, phase difference
2 deg. Then, it will give you 35db image rejection ratio.

Where I can get it?
Thanks,

IMRR=10*log10((2*pi*phase/360)^2/4+(10^(amp/20)-1)^2/4)

IMRR: Image rejection ratio because of

phase: Phase imbalance

amp: Amplitude imbalance

An expression found in Razavi but could be also derived by longer math derivation negleting higher order terms.