Hi!

I have been using ADS Momentum for some time now and there is a behavior of the software that drives me nuts.

I am using Adaptive Sweep and for rather large structures momentum for some reason uses lots and lots of its adaptive points in a small interval around 19 MHz. Sometimes almost half of the frequency points are in this small interval (+/-1 MHz) even though the complete interval is 0 GHz to 50 GHz.

I assume that this has something to do with DC(?) convergence? I have tried to combine adaptive sweep with other types (linear) but then runs into another problem where the interpolation between simulation points is extremely strange (passes through center of smith chart).

Any ideas?

I have been using ADS Momentum for some time now and there is a behavior of the software that drives me nuts.

I am using Adaptive Sweep and for rather large structures momentum for some reason uses lots and lots of its adaptive points in a small interval around 19 MHz. Sometimes almost half of the frequency points are in this small interval (+/-1 MHz) even though the complete interval is 0 GHz to 50 GHz.

I assume that this has something to do with DC(?) convergence? I have tried to combine adaptive sweep with other types (linear) but then runs into another problem where the interpolation between simulation points is extremely strange (passes through center of smith chart).

Any ideas?

I have actually tried exactly that: "The latter issue can be avoided my making the AFS simulation 100 MHz to Fmax and then adding a discrete point at DC" and it solves the 19 MHz issue but I then ran into another problem.

The discrete point that I added at 0 GHz is present in the data set but the s-parameter simulation that I am running on the momentum component does not recognize that point and gives the following error "S-parameters are not available at 0 GHz".

The interpolation in the _a data set between 0 GHz and 100 MHz also looks very strange as it includes the center of the smith chart.

Thanks in advance.

I have experimented with different settings in the sweep dialog and got quite successful with adding to separete adaptive sweeps. One between 0 - 11 MHz and the other between 29 - 50000 MHz. As these sweeps does not contain the 19 MHz point I am able to run a simulation without any problems related to that problem stated earlier.

What I really can not understand is why the interpolation between 11 and 29 MHz is so strange. I wish I could attach an image to show you. Both the 11 and 29 MHz points are kind of close to the edge of the smith chart and very close to each other. Unfortunately the interpolation insists on including the center of the smith chart in the interpolation. I guess that this is due to the fact that the interpolation is linear? Is this how it is intended to be?