flyhigh said:Hi,
just to add something about Lange couplers in general. To my experience (some but not impresive) wire bonds are the main source of difference between simulations and measurements. No matter how you model them in EM simulator they tend to be different in a real circuit. So, wire bonds could add some parasitics that are out of control.
flyhigh
Grig said:OK, Max
And what do You think --- Side walls , substrate edges can produce different coupling or not?
I know that for narrow band filters enclosure effect exists (and was published)...
What's about accuracy of ADS2004 momentum modeling of thick metal current distribution.
I have understending that multiple measurements on number of structures needed to have unswer, but have no possibility for such measurements. (Then I must ask anybody).
Thanks
maxwellian said:I have found that more of the differences between modeled and calculated are due to whether or not the model in the EM simulation took into account metal thickness, more so than how the wirebonds were modeled. I suppose that if you are using very high wirebonds or very wide (or multiple side-by-side) flat ribbon bonds for a design, you could add some amount of extra phase in them to throw the results off a bit, but I think in practice most people keep these short enough. There might also be some issues if you're not very accurate about the placement of the wirebonds.
--Max
flyhigh said:This is generally true, however the acctual influence of wire bonds is dependant on operating frequency as well. Alumina is high dielectric constant substrate and the bonding effects at 2GHz might be neglected but at 25GHz they can play a role.
Of course, one can change the substate to lower dielectric constante to make these effects secondary again.
If you model (mesh) finite metal thickness and are sure that it is most significant cause of discrepancies, than you also might need to take into consideration the acctual shape of the edge (underetching, overetching, line width/slot width variations etc.) as this is obviously critical. Depending on the technology available and the price one can afford, edges could look really scary under the microscope! I think this should also get worse with increasing substrate dielectric constant.
flyhigh
Grig said:Hi, flyhigh
I'm agree "one should be realistic about the differences of simulated and really made circuit " but one should understand which factor gives 1dB which gives 0.2dB
Is there any book or article about such analysiz?
Can You propose some book about "philosophy of modeling the nature by humans"?
Thanks
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