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Hyperlynx differential impedance calculation mistake

Question asked by vova2211 on Oct 10, 2016
Latest reply on Oct 10, 2016 by vova2211


I'm simulating an exported from Altium designer 16.1 Rigid Flex PCB board, which contains suppose to be 100 ohm diff pairs  . The Hyperlink calculates its Zdiff as 82 ohm for some reason .

1. The designed PCB with correct PCB stack-up and Diff pare parameters where set in the Altium .

2. Exported as HYP file from Altium and opened in Hyperlynx V9.4 .  All passed well, with correct traces drawing and layers stack-up . The ref / signal planes were selected .

3. The selected diff traces where extracted from BoardSim to LineSim , in order to review a transmission lines topology and impedance.

Somehow, the calculated by Hyperlynx differential embedded microistrip impedance is 82.1 ohm, while it suppose to be 100 ohm according to its layers stack-up and Er.

Attachment 1.jpg - screen of LineSim with all the related  geometric parameters of transmission line with a wrong calculated Zdiff.

Attachment 2.jpg - the correct calculated Zdiff by two known impedance calculators using the same trace and stack-up parameters.

Where is my mistake ?