#1930

Episode 1930
laying out an impedance controlled PCB
APPCAD: www.broadcom.c...
Be a Patron: / imsaiguy

[@eGnarF]

Kicad has a built in calculator that can solve for the width of the stripline.

[@p.1206]

It can be pretty inaccurate compared to a 2D field solver. Might be a good video idea to compare calculators.

[@ianhasnochannel]

At those trace lengths, the width shouldn't matter at all. General rule of thumb I've always heard was 1/10 the wavelength, so at 1GHz, width of traces under about 30mm doesn't make much difference.

[@MrXenon1977]

With slower propagation speed the wavelength gets shorter...

[@bobdoritique7347]

Merci for this video. Very interesting material considerations.

[@NikiBretschneider]

I often prototype things like this using an adhesive copper tape on a single side plated FR4. It's easy, because the copper plating gives me a ground plane while the adhesive copper tape is used to build an actual circuit (as it's easy to cut using scissors and also easy to modify if something goes wrong). And I know that 100mils is almost perfect for Z₀=50Ω, but it's also relatively easy to measure Z₀ of transmission line as long as you have a VNA, so you can easily check your calculations in a real world scenario. The easiest way is to measure the transformation of a ¼λ transmission line (which is easy to build using that copper adhesive tape), which transforms real loading impedance to another pure real (non complex) one, which is easy to find using the VNA (it crosses the horizontal line in the smith chart and it's different to the loading impedance). Then Z₀=√(Z(in)·Z(load) and you can also calculate the propagation delay, because you know on which frequency you have a λ/4 transmission line and you also know its physical length. …and sometimes you realize that what was claimed to be a FR4 is in fact far from being FR4. That calculator inside KiCad is worth to try, because it can both syntetize and analyze your transmission line. In fact, it's a powerful and handy thing.

[@IMSAIGuy]

kzbin.info/www/bejne/h5mxqKKFhpZojK8si=O1FNCrZc8q4gE1JU

[@edmaster3147]

Thank you.

[@herbertsusmann986]

It would be interesting to also make this using a Teflon board and see if there is any difference up near 6 GHz compared to the FR4 board.

[@danishnative9555]

Please do some boards on Alumina ceramic and RT Duroid so we can compare the results. TNX.

[@garrytaylor5471]

The inductor should be about 500 ohms at the desired frequency of operation.

[@dilbertnewton6864]

Are there any rule of thumb for using the gnd stitching vias?

[@IMSAIGuy]

others can comment. I just do what feels right

[@BarryM-y3m]

Does the Imsai dog bite?

[@MaxPivovarov]

It's not right trace, u must ended it without rounding, but only 45 degrees corner.

[@willthecat3861]

Is he using ADS?

[@IMSAIGuy]

no

[@BarryM-y3m]

Does the Imsai dog Bite?