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frequency divider simulations in ADS(?!?)

Question asked by zheshmat on Nov 9, 2005
Latest reply on Nov 10, 2005 by zheshmat
I am trying to simulate a varactor frequency divider (which I have build and tested in the lab) in ADS. It contains nonlinear capacitances (varactors) as well as balanced microstrip coupled lines. I have tried both Transient and HB as well as TAHB - but I cannot successully simulate the circuit to see the half frequency.

From the documentation, I understand that in order to use HB, or in this case TAHB, we must have a Transient simulation that works and reaches steady-state, so that we can use it in TAHB. But I have convergence problems even in the Transient simulator. Whatever I change or edit, I keep getting the same error message that "internal timestep too small at time ....". I have tried changing MAxTimeStep, Time Step Control Method, Integration, Convolution etc. ... but still get the same error message. Occasionally this disappears and the simulation finishes without errors but it's not consistent.

Can you please guide me as to what I can do to eliminate these convergence errors and to get a close enough simulation to the measured data?

[NOTE: The divider circuit has a threshold level on the input power and very dependant on the nonlinear elements - could this have anything to do with the problem?]  

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