Does anybody here have experience with RF PCB design? And maybe would be interested in a small bit of consulting? Comment here or send me a PM.
I have done some simple stuff, but usually I would get help on the RF part of PCB I would design at my last job. It really depends on what your trying to do. Sometime you can get away with something really simple. When pushing the limits, you may need an expert. If I cannot help, I maybe able to put you in contact with someone who can.
I’m building a PCB with a 2.4ghz wireless connection and a u.fl antenna connector. The board is small and the traces are short. I have some recommendations from the chip documentation, but it’s pretty much impossible to follow all the guidelines.
The guidelines calls for 0.71mm traces, and also 0.71mm spacing around the traces, and it is basically impossible to accommodate that. Right now my spacing is about 0.4mm, and I don’t know how big of a problem that is. The traces are only a few mm long after all…
I could order a PCB and measure the complex resistance, but I also don’t really have the experience to know how close it has to be to work.
Do you have access to a RF network analyzer to measure the impedance (complex resistance) of the PCB transmission line? I usually skip this, since it is not useful for small traces, about wavelength/20, which is about 6mm for 2.4GHz in air and less for PCB. Please, check my math.
I would just get ISOLA FR408-HR PCB using Oshpark 4 layer. I don’t think their other PCBs are good for RF. If the device works with the range you want, then you are done. For 2.4GH or less this usually works.
Does the guidelines call for microstrip vs coplanar waveguide? If you point me at the datasheet. I should be able to tell you what the trace widths you should use for Oshpark 4 layer. Many people use ISOLA FR408-HR for 2.4Ghz, so we should be able to skip the impedance measurement.
I have a LiteVNA, which is a cheap instrument, but should be able to to do the job.
I currently have ~7 mm of traces between the chip and the antenna connector, some of which is a balanced signal, which might be different. (or not? I don’t actually know) The chip has two outputs, which goes to a coil, after the coil there is an in-line capacitor, and then the signal goes to the antenna connector. Each component adds ~2mm of traces.
The guidelines just says to adapt your calculations for microstrip vs coplanar. My PCB currently uses a microstrip design.
Oshpark 4-layer isn’t an option for this board since it needs blind vias (layer 1-2 and layer 3-4).
Do I sense an ESP32-based Proffieboard on the horizon…?
Hi Fredrik,
I have a solid background in RF PCB design, worked on both low-noise and high-frequency layouts across a few industries.
Happy to help with consulting on your project if youre still looking.
I can review your design, suggest layout improvements, or assist with impedance matching and stack up choices.
You can reach out to me on my email here
Colin
Well met Colin, I’ll be sending an email shortly.
A thought occurred to me though:
I don’t suppose I can gain the knowledge I need for this by reading a book?
If so, what book would that be?