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Harmonic Balance Sim of Layout Component - Choosing Order

Question asked by kippodan on May 22, 2014
Latest reply on May 22, 2014 by aehoward
Hello everyone!

I have a layout component that I simulated in ADS momentum uW which contains the metal layers of my circuit and then I perform a HB sim on the circuit. Let's say my fundamental frequency is 10 GHz (the frequency of interest). Initially I simulated in momentum from 5 to 15 GHz but my results were not what I expected so I simulated up to 20 GHz and got something much more reasonable. I'm assuming this is because the HB did not "see" any harmonic frequencies in my model?

That leads me to my first question: Does that mean that I need to perform an S-param simulation in momentum up to the order indicated in the HB sim? For example if I use an order=9 for the HB then I would need to simulate my layout up to 100 GHz to obtain realistic results? This seems reasonable to me but it's not very practical for me to simulate up to these high frequencies because then the distance between the + and - terminals of my ports become electrically large past 20 GHz or so. Still, even if I only simulate up to 20 GHz but use a higher order for the HB sim I get "smoother" results but then where is ADS pulling the data from on these higher frequencies? And can these results be trusted?