You seem to have no experience of actual measurement at all.
You have to learn measurements using actual instruments. Not "EDA Tool Play".manfred wrote on Mar 22nd, 2009, 4:01am:"the practical value" is the right gain from transient simulation or pss simulation, which i think is right.
Maybe your gain definition of PSS and Tran is Vout/Vin.
You don't understand various voltage gain definitions.
Gain definition of Direct Plot is same for PAC, PXF and Pnoise, which is not Vout/Vin. Gain definition of PSP is Vout/Vin. S21 is another voltage gain.All these gain are "right" and "true" voltage gain.Actual NF meter give gain and NF values at same time.
Do you understand definition of this gain ?
manfred wrote on Mar 22nd, 2009, 4:01am:about 6dB greater than the true voltage conversion gain, I think it is caused by vout/E (E is my setup in port),
Correct. But it is never 6dB. And an expression of "
the true voltage conversion gain" is not proper.
Gain from PXF is also
true voltage conversion gain.
If you dare to refer Vout/Vin with some name, you should call it as general or common voltage gain which is used for low frequency circuit.
manfred wrote on Mar 22nd, 2009, 4:01am:but in reality, the signal at the gate of mosfet is 2E, so the gain from PXF is 6dB. is it right?
It is a little wrong.
Input impedance of DUT is not infinite actualy. For high frequency it is capacitive at least.
So It is never 6dB actually.
Your usage of symbol "E" is not common.
Generally "E" is used like following.
See
http://www.designers-guide.org/Forum/YaBB.pl?num=1122952471/2#2Your usage
Quote:I think it is caused by vout/E (E is my setup in port)
the signal at the gate of mosfet is 2E
Common usage
Quote:I think it is caused by vout/(E/2) (E/2 is my setup in port)
the signal at the gate of mosfet is E
manfred wrote on Mar 22nd, 2009, 4:01am:if I parallel a 50 ohm resistor to the port , I can get the right conversion gain from PXF
Not correct.
It is not right gain at all.Again input impedance of DUT is not infinite actualy. For high frequency it is capacitive at least.
manfred wrote on Mar 22nd, 2009, 4:01am:but I still wonder about the true NF.
if I parallel a 50 ohm resistor to the port , I can get the right conversion gain from PXF,
but the NF from Pnoise is not right, because the resistor introduce extra 3dB noise.
You are completely wrong.You can't get even correct general voltage gain in your method. Of course you can't get correct NF.
You don't seem to understand RF basic theory at all.
You should read text book on RF Basics.manfred wrote on Mar 22nd, 2009, 4:01am:so, can you tell me how should I do in order to get both the right gain from PXF and right NF from Pnoise?
If you want to calculate Vout/Vin, use one from the following three methods.
(1) Don't place 50 ohm resistor parallel to port. Invoke PSS/PAC/Pnoise.
About NF, use Direct Plot for Pnoise.
Calculate Vout/Vin from PAC without using Direct Plot.
(2) Don't place 50 ohm resistor parallel to port. Invoke PSS/PSP.
You can Calculate both NF and Vout/Vin from PSP by using Direct Plot.
(3) If you want to insist on using PXF, place 50 ohm resistor of noiseless parallel to port and use VCVS to drive DUT. Invoke PSS/PXF/Pnoise.
You can calculate both NF and Vout/Vin by using Direct Plot.
But I never use this method especially for mixer. See the following.
http://www.designers-guide.org/Forum/YaBB.pl?num=1231854969/5#5Indeed I don't calculate Vout/Vin since we can't measure Vout/Vin in actual measurement.
I calculate different voltage gain which is matched to definition of actual measurement.
Many Cadence Tool Players have same confusions as you have.http://www.designers-guide.org/Forum/YaBB.pl?num=1214890959/2#2http://www.designers-guide.org/Forum/YaBB.pl?num=1194006190/2#2This is due to no experience of actual measurements of Cadence Tool Players.
On the other hand, Agilent Tool Users(not Players) never have confusion for such too basic issues since almost of them have experience of actual measurement.
Again, you have to learn measurements using actual instruments. Not "EDA Tool Play".manfred wrote on Mar 22nd, 2009, 4:01am:thanks for your patience!
I'm not kind and patient enough for explaining such too basic issues.
If you can not still understand, other people who is very kind and patient will help you.
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about "port" when simulating mixer without input impedance match (Read 11671 times)