●●● ●●●● ●●●● ●●●● 2.Image Frequency ●●●● ●●●● ●●●● For down-conversion frrl=fio+fiF,fRE2=fLo-fr They are indistinguishable at the IF stage,unless to reselect the signal and stop the noise or interference.它们在 中频没有差别，需要预先选出信号，抑制噪声或干扰， ② fio=fs±fiF noise of LO 本振的噪声 ③ f1o-fRF =fv fiu-fLo=fLo-fRE Two times mixing二次混频 fLo is the two times harmonies of LO,coming from inside or outside of mixer.f方Lo是本振的二次 谐波，来自于混频器的内外 62. Image Frequency ① For down-conversion They are indistinguishable at the IF stage, unless to reselect the signal and stop the noise or interference. 它们在 中频没有差别，需要预先选出信号，抑制噪声或干扰. ② noise of LO 本振的噪声 f2Lo is the two times harmonies of LO, coming from inside or outside of mixer. f2LO是本振的二次 谐波，来自于混频器的内外 ③ Two times mixing 二次混频 10 20 , RF L IF RF L IF f f ff f f    L RF IF 0 fff   f20 I L RF M   f f IM L L RF 0 0 ff ff    6