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32 I-CONNECT007 MAGAZINE I APRIL 2026 coupon generator, but for that reason, we haven't done it, as it might mean the hatch on the coupon hatch is created differently from the hatch under the circuit itself. How Did the Variation Arise? I started by noting that a customer reported dif- ferent impedance results from the same modelled data than from their supplier, so I took a long, hard look to see whether units were mixed or there had been some form of input error. But as hard as I tried, I could not replicate the discrepancy. My numbers only aligned with one of the predic- tions sent to me. Then, as with all detective work, T H E P U LS E Figure 2: Figure alignment is the ideal situation, but not always possible. a minor point struck me that I had missed on first look: One of the screenshots had a "+" and a "–" in the top left of the structure image (Figure 3). The other image from the OEM's supplier did not contain that control. A look in the archives showed me that this change in our software dated one version at a release (at least 11 years older than the latest, maybe 15), which was in the early days of crosshatch modeling for Polar. Our tools are regu- larly updated and fine-tuned, and so I find myself now in a further search to see what has changed and what might have improved since those early days. A lesson, perhaps, in making sure that soft- ware is regularly updated, especially when work- ing on critical designs. So, as with many investigations, the original sup- position turned out to be wrong, but it did point to further analysis and triggered the search for the cause of the difference. I-CONNECT007 Martyn Gaudion is managing director of Polar Instruments Ltd. To read past columns, click here. Martyn is the author of The Printed Circuit Designer's Guide to… Secrets of High-Speed PCBs, Parts 1 and 2, and The Printed Circuit Designer's Guide to…More Secrets of High-speed PCBs. Figure 3: Detective work led me to find a plus and minus sign in the top left.