Strange results when simulating EM structure with Transient in ADS2012

Hi all,

I have found a strange case. In my schematic simulation in ADS2012, I have an EM structure (say a Balun) simulated together with other components in this schematic. Then I simulated S parameters, I recorded the insertion loss of this Balun (say S21 = -3 dB). Then I changed to transient simulations. The results showed me that the the loss of the Balun is much lower than 3 dB obtained from S parameter simulation.

Then, I changed the simulations to AC and HB simulations, after I checked both transient waveforms and amplitude spectrum, I got the results very close to 3 dB.

How come that EM structures gave very strange results in Transient simulations !!! ??

I also found this strange results in other circuits that I use EM structures with Transient simulations.


Thanks a lot,

DYL