假设Rf:
Cos(Rf)
单音音频信号Af:
Cos(Af)
先给Rf做移相得到IQ信号
Rf_I: Cos(Rf)
Rf_Q: Cos(Rf+Pi/4)=Sin(Rf)
然后给音频信号移相得到IQ信号
Af_I: Cos(Af)
Af_Q: Cos(Af+Pi/4)=Sin(Af)
然后交叉混频
Rf_I*Af_Q = Cos(Rf)*Sin(Af) = 0.5(Sin(Rf+Af)-Sin(Af-Rf)) = 0.5(Sin(Rf+Af)+Sin(Rf-Af))
Af_I*Rf_Q = Cos(Af)*Sin(Rf) = 0.5(Sin(Rf+Af)-Sin(Rf-Af))
USB是结果的和
USB = Rf_I*Af_Q + Af_I*Rf_Q = Sin(Rf+Af)
LSB是结果的差
LSB = Rf_I*Af_Q - Af_I*Rf_Q = Sin(Rf-Af)
如果是两者直接混频是DSB信号, USB+LSB的
Cos(Rf)*Cos(Af) = 0.5(Cos(Rf+Af)+Cos(Rf-Af))
貌似不交叉混频也可以,得到的结果是cos的
Rf_I*Rf_Q+Af_I*Af_Q ,混出来是LSB = Cos(Rf-Af) = 0.5(Cos(Rf+Af)+Cos(Rf-Af))+0.5(Cos(Rf-Af)-Cos(Rf+Af))
Rf_I*Rf_Q-Af_I*Af_Q 混出来是USB = Cos(Rf+Af) = 0.5(Cos(Rf+Af)+Cos(Rf-Af))-0.5(Cos(Rf-Af)-Cos(Rf+Af))
[ 此帖被BI7LNQ在2012-05-14 20:43重新编辑 ]
