The circuit in Fig. has two signal paths: one is M1—M3—Vo2, the other is M2—M4—Vo1. And the two paths have the same voltage gain, but impedances are different.
To measure S-parameters I have connected balun from rflib.
But my doubt is
(1) Should I use buffers before balun to match impedance, since V01 and V02 impedances are not 50ohm?
(2)If I use buffers, I think it will effect the S21 and NF. So is there any other ways to measure S-parameters of this kind of circuit?
Please help me in this regard ....
Thanks in advance....
It seem to me that you have to measure the output in differential mode. To do that, you can put a floating resistance (matched to the LNA differential output impedance) and measure the power transmited to this resistance to extract the single to differential S21.
Dear Sir(Damien Prele)
Then what about measurement of remaining S- parameters and noise figure.
Actually we used to connect two ports i.e, one at input and other at output side to measure these parameters.
Dear Vasudev!
I saw your circuit diagram and have the feeling there is something not in order. Can you explain the operation of this circuit. The circuit seems as differential cascode. But how the input is applied? I would make spice circuit analysis before calculating the S-parameters.
wish you success
Dear Sir (Abdelhalim Zekry )
I am extremely sorry to saying that there is a mistake in the circuit diagram which I have uploaded. Actually input is applied to source of M1 and gate of M2. The source of M2 is connected to ground (But it is connected to input in the uploaded figure). It is kind of single input -differential output configuration.
Here I am attaching the circuit diagram.
Dear Sir (Abdelhalim Zekry )
I am extremely sorry to saying that there is a mistake in the circuit diagram which I have uploaded. Actually input is applied to source of M1 and gate of M2. The source of M2 is connected to ground (But it is connected to input in the uploaded figure). It is kind of single input -differential output configuration.
Here I am attaching the circuit diagram.
Dear Vasudev,
welcome!
First today i saw your last comment.
The input is single ended, so you can measure its parameter.
As for the differential output i would propose that you have two output ports one with positive phase and one for the negative phase.
Assume that these output ports out1 and out2
every port has its S-parameters S22 AND S12 as well as S33 and S13 where 1 stands for the input port.
Best wishes
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