low-IF mix=NF(SSB),0-IF mix=NF(DSB),low-IF + 0-IF=??

[wccheng]

Dear all,

I have one question about the NF value simulation in mixer. In my design, it consists of two down-conversion mixers. First one is low-IF mixer and second one is zero-IF mixer. In the simulation, I simulate the low-IF mixer and get the NF(SSB) value. At the same time, I simulate the zero-IF mixer and get the NF(DSB) value. If I combined two mixers together and run the simulation, which NF value is correct, SSB or DSB?

Thanks

wccheng

 

[kspalla]

May I know the tool name please?
In ads you will get with nf(2)

 

[wccheng]

Spectr..

 

[kspalla]

In my view,
Both are correct. Note that the upper base band frqency of zero IF is not overlapping with lowest posible frequency of lowIF.
There will be sufficient filtering stages in IF and in Digital domain.

The next stages determine the NF calculation.
let say the further processing is at low IF then the outcome of zero IF is not usefull as they will be filtered in further stages.