serenade simulateur

hi:

I would like to know the difference between using the ideal transmission lines (electrical) and the microstrip transmission lines (physical) in serenade.
I used the electrical lines and I got S11 = -3.96 dB (based on mismatched input), S21 = 6.96 dB (out of 7 dB) and S22 = -44 dB.

With physical lines, I got S11 = -4.91 dB, S21 = 7.22 dB (bad) and S22 = -17.56 dB

I put the substarte media (microstrip) with Er = 2.2, tanD = 0.0009 and H = 0.78741mm (using RT/Duroid 5880). Also the copper thickness
(34 um)was given but I didnot include it in the substrate media. i tested it once with the copper thickness and i got almost the same results. Are there anything else goes in the substrate media?

Can I know why the results are different?
frequency was 5.5 GHz using BJT. width of trasmission lines was 2.43 mm and lembda = 3.987 cm, Eeff = 1.871

In fact, the expected results (from theory) match those of the electrical lines.

thanks
ayhz2002

Here are some guesses on the source of the problem.

1. Going from electrical to physical and then from physical to electrical for the overall simulation. (cumulative errors)

2. Line loss adds to the S parameter values.

3. End effects from changing the conductor width in going from the transmission line to the transistor tabs may not be taken into effect in the electrical models but is in the physical models. (shunt reactance at step in width)

I just want to add another point...

Ideal tr line dosen't radiate and no coupline between two lines but microstrip line radiates and always have coupling between two tr lines. In sernade most probably the mutual coupling is neglected but radiation is taken care of.