What causes my simulation so inaccurate?

[John_li]

Dear friends,
I want to design LNA.I want to estimate the via effect of the source to GND.I use the FR4(1mm sub,35um cond) and via(pad diameter=0.7mm,drill size diameter=0.4mm),i simulation by ADS,and get the value L=447.6pH,when i meaure the via,i only get L=1.0886nH.
Now i attach my simulation and measured result,any friend can tell me the root cause?



Thanks,

 

[biff44]

44 nh is at least a factor of 10 too big for the via hole inductance. I would look closely at the via hole input numbers, and see if you have made an entry error.

A via hole is not modeled fully by just an inductance to ground, there are stray capacitances, some line length, etc. too.

 

[Chinaski]

Just watching the results (dds file) , inductance reads 0.45 nH (4.47e.10) not 44.7 nH.

 

[John_li]

Just watching the results (dds file) , inductance reads 0.45 nH (4.47e.10) not 44.7 nH.

Thanks and sorry that i made a mistake.Now i correct it.It is inaccurate .

Added after 21 minutes:

44 nh is at least a factor of 10 too big for the via hole inductance. I would look closely at the via hole input numbers, and see if you have made an entry error.

A via hole is not modeled fully by just an inductance to ground, there are stray capacitances, some line length, etc. too.

Dear biff44,
I only use only one via to simulate with momentum to compare the simulated result with measurement.
Thanks,