Hi,
I'm looking for some help in a field that is super technical and I don't fully understand.
I'm planning on using a bunch of these seeed studio Esp modules for some home automation projects, especially because they have a lipo battery charger making it great for portable stuff.
The thing is the the ESP32s have U.FL SMD antenna connectors. Most of the antennas that you can buy with U.FL connections while are reasonably small, come with 50-150mm leads, which sort of makes the small size of the module a little less valid.
What I'd like to do is get a female U.FL SMD connector and make a small daugherboard with an 2.4GHz SMD antenna on it, for instance a Janson 2450AT42B100 or a Molex 479480001.
They go over the circuit board requirements quite thoroughly so I don't think designing it will be too difficult, but what I don't know is, they say that you need impedance matching on the circuit, and I see that there appears to be something that looks like it on the ESP circuit diagram, but I'm not actually sure if it is or not:
You can see it in the middle near the bottom of the diagram here: Seeeduino-XIAO-ESP32C3-SCH
So my questions are:
1: Is this a dumb idea, having a direct plug-on SMD antenna?
2: Is that an impedance matchning circuit between LNA_IN on the ESP chip and U.FL-R-SMT-1?
3: If I can't get a female U.FL SMD connector, would using one with a lead and shortening it to make the daughterboard able to be much closer to the connector affect anything? Do I need to ensure that the lead length matches the wavelength at all?
Edit: Found this SMD female U.FL, so they do exist.
antenna design is usually limited by one of these things: size, gain/radiation pattern, efficiency, bandwidth (fixed here, entire 2.4ghz band)
you can probably use off the shelf antennas used for drones if these are small enough for your application
soldering coax can be tricky, don't melt center insulation. you'll need to size microstrip line so that it'll have impedance 50 ohms as well https://www.pasternack.com/t-calculator-microstrip.aspx
Thank you for your detailed reply, I really appreciate it. It answers my question and raises a whole bunch more :D, I think I need to brush up on general RF and get a better understanding of how it actually works. I shall do some youtubing and reading on it. I found a really good pdf that discussed antenna design but a lot of it I didn't understand, so I'm going to need to learn a bit more.
Ill also take a look at the drone antennas too.
Thanks again for your help.
if you want to measure anything rf, you'll need a vector network analyzer like nanoVNA (some $40), this will be very useful in tuning/matching antennas (and making sure you won't get reflections that could potentially damage transmitter if you screw up badly enough)
This all seems really complicated but at the same time super interesting. Thanks for the recommendation.