Can I get the dc resistance of this EM-simulated-inductor from its S2P file?
Yes, it works and you can get accurate results when using Momentum RF mode. I use this all the time for RFIC inductor work.
For evaluation, you can use your circuit, or you can calculate series resistance in the data display from Z-parameters using equations. Below are equations that evaluate the path between port 1 and port 2 (differential operation).
View attachment 147676
Extracting DC resistance from EM model may be erroneous.Because even though EM simulator covers 0 Hz ( DC ) in fact the simulator starts from very low frequency but not exactly 0 Hz.
Your method will not work-absolutely..
Extrapolation ( down to DC ) may work but it can also not give the "exact" resistance, just approximated value can be obtained..
The better way is to calculate DC resistance by well known method.( Sheet resistance technique )
Thanks for the information! I tried your equations, it gave same result as using the circuit. Your mentioned that I can get accurate results from Momentum RF mode, how about Microwave mode? Would be result be similar?
For manual calculation of DC resistance, you just add all the metal sheet resistance * length / width and also add the via resistances. This is a good test to check EM solver results at DC.
the metal sheet resistance in ohm/square(which is equal to ohm right?).
My calculated DC resistance is 1.8ohm compared to 0.7ohm in EM. and the schematic inductor gives 3.5ohm. that's a lot of difference. Any thoughts?
I assume you are also working on RFIC inductors, not PCB?
That's a great feature to know! Thanks! the via is Au(resistance should be minor right?). Just re-ran the inductor with your info, result looked similar but definitely not exact.Since ADS 2016, there are some advanced features to keep the area when doing via merging.
ohm/square is the resistance of a square segment. If that value is 10mOhm/square and your inductor turn length is 1000µm and width is 10µm, then resistance is 10mOhm * 1000/10
From my experience, Momentum DC results are very close to manually calculated data, so your difference is unexpected. Maybe your path length is wrong or the vias are missing or there is a mistake in the EM model. All values should agree much better.
Your simulations look great comparing to measurement. Just not to be confused. The effective resistance in your graph is DC+AC resistance right?Below I have attached an example what I get for measured vs. simulated in RF mode (2.8nH in IHP SG25H technology).
the via is Au(resistance should be minor right?).
The drawing trace is the length I added up = 3200um. width of trace is 25um. and Rs=10mohm/sq. Without via resistance, I am still getting 10mOhm*3200/25=1.28ohm which is big compared to 0.65ohm result. Am I adding the path length correctly?
Your simulations look great comparing to measurement. Just not to be confused. The effective resistance in your graph is DC+AC resistance right?
I am also trying to understand the equations you provided. Why omega and Zdiff are needed? Would it be okay just use Z-parameters?
Sounds like some III-V technology? I am working on SiGe/CMOS technologies where via resistance can be very significant for narrow lines where the via array is small.
I double checked the metal thickness and its resistivity. They seem reasonable. I have so many things in the workspace, and I am trying to look for a way to simplify it! I exported .gds and its substrate. Need a way to put in material definitions.The shape of your simulation result, with the drop below 2GHz, looks a bit unusual. I would rather expect the curve to flatten towards lower frequencies. Can you copy this model into a new workspace, and upload it here?
I am trying couple ways at this point. I tried Zin from s-parameters to get its real part at DC, but doesn't seem working. The dc resistance does not match to you method. I also tried simulate Z-parameters, but I do need your Zdiff equation. Could you please explain Zdiff and why it should be used?I want my equations to also work with imported S-params, where the dataset does not include "freq" variable and Z-parameters. That's why I get the frequency as indep(S) and create Z-params from the S-params.
I double checked the metal thickness and its resistivity. They seem reasonable. I have so many things in the workspace, and I am trying to look for a way to simplify it! I exported .gds and its substrate. Need a way to put in material definitions.
I am trying couple ways at this point. I tried Zin from s-parameters to get its real part at DC, but doesn't seem working. The dc resistance does not match to you method.
I also tried simulate Z-parameters, but I do need your Zdiff equation. Could you please explain Zdiff and why it should be used?
Zin should be the inductor in series with the 50 Ohm at port 2.
If you look at my appnote here (section "Why are these results different?"), you will see that results are indeed different, because the parasitics from the substrate network have different effect.
For DC, results for single ended and differential R and L are the same. For RF frequencies, you might select single ended or differential parameters depending on your circuit use.
which is pretty close to 0.7 of my EM. That was my stupid mistake!!
Does it mean that R_dc = the DC point of Zin - 50ohm?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?