Impedance calculator?
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martin 2 months ago
Hi, this page: [https://cart.jlcpcb.com/impedanceCalculation](https://cart.jlcpcb.com/impedanceCalculation) is intended to be used as an impedance calculator. I am not sure how it's supposed to work as there is no field for frequency of operation!
andyfierman 2 months ago
The board thicknesses are given in mm so it is not clear that the required units for trace width appear to be mil (0.001 inch). It would be nice to have a mm/mil switch including the board thicknesses.
andyfierman 2 months ago
@martin, Why do you expect to see frequency in a trace impedance calculator? The type of calculator offered by JLCPCB is to calculate characteristic impedance of (a limited set of) PCB transmission line structures. To first approximation, transmission line impedance is independent of frequency. As the signal frequency increases losses in the dielectric (substrate) and copper (skin effect and surface roughness) increase but the characteristic impedance is more or less constant. If the signal frequency is so high that all the above effects start to matter then you should not be relying on a simple calculator but should be using tools like MWI: [http://blog.rogerscorp.com/2018/07/12/calculate-microwave-impedance-with-transmission-line-modeling-tool/](http://blog.rogerscorp.com/2018/07/12/calculate-microwave-impedance-with-transmission-line-modeling-tool/) or a multi-layer dielectric field solver tool such as mdtlc: [http://mdtlc.sourceforge.net/](http://mdtlc.sourceforge.net/) If you want to calculate the complex impedance of a given trace at a specific frequency for example if you want a piece of track to present a given impedance to an RF power amplifier or as part of a filter then a PCB transmission line calculator is the wrong tool because that is not what they are set up to do.
martin 2 months ago
@andyfierman, I will plainly admit a brainfart. Chalk it up to too many Smith chart antenna match calculations! ![image](https://media3.giphy.com/media/4bpK2k0Yru5Us/200.gif)