Hi,
I am designing a VHF band mixer, and I am confused about the result:
The apps eng use following eq to calculate the output noise for each stage:

sqrt(K*T*R_source) * voltage_gain_linear * sqrt(NF-1)

then rms w/ the product of previous stage's output noise and current stage gain to get overall noise
it makes sense when input source marchs Zin of mixer, because source noise sqrt(4KTR), V/sartHz, will make sqrt(KTR) at input of the mixer, but my mixer input is HiZ, then when spectre report NF (pnoise + pss), it is "marched NF" or not? in other word, when spectre calculate NF form output noise contributor %, it set noise voltage at mixer input to sqrt(4KTR) or sqrt(KTR)?

If it use sqrt(4KTR) at input, I guess it does because that is what the circuit is really doing then above eq to calculate output noise is not valid anymore?

Thanks
Jun