Question on PORT reference and Z-port value in Ansys Circuit Nexxim - Inconsistant results between Transient and linear analysis ...

[rdpdo2002]

Hello,

Under Nexxim, when I configure my port 1 (Z=0, with reference to GND) with a sinusoidal source 1Vpp 4MHz and my port 2 (Z=10e9, with reference to GND) I got about G=-3db using Nexxim Transient Analysis :

So tell me if I am wrong, but for what I undertsand it's like having this :

Now When I remove the sin source on PORT1 and do a LNA 0-20 MHz, I got this. I still get the -3 db at 4MHz but offset by -140 db ...

For having good result, I need to reference PORT2 to PORT2 himself, using a Z=0 :

Why do I don't get same result using LNA and transient analysis when PORT2 is referenced to GND with Z=10e9 ?

Thanks you !

 

[BigBoss]

You do an s-parameters simulation, and one port is short circuited, other is open circuit.
What exactly you've been expecting ??

 

[rdpdo2002]

You do an s-parameters simulation, and one port is short circuited, other is open circuit.
What exactly you've been expecting ??

I don't understand why the same port2 configuration give me different result when I do LNA and when I do simple sinusoidal freq analysis ?