I'm sorry very late.
I tried many things for finding difference between HB and TRAN.
I checked other components.
R, C, L show same results.
But transmission line and transistor show differences.
I attach results of transmission simulation.
I made a very simple circuit for test.
This S21 exactly same with result of SP-Sim.
left is HB ans right is TRAN results.
I tried to deduct same Vout, Vin, Power Gain, very hard to me.
Is there some errors ? or mistakes ??
I don't know why transmission line and transistor have difference between HB and Transient.
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i attach other result(change to 50ohm transmission line)
<- this is HB result
<- Transient result
i think i miss something when simulate transient sim ..
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And I find some problem.
it's okay until 250GHz.
but 250.1 GHz , it's strange