Hi Dave,
1- I've upload the Kicad project as a zip file.
2- I also upload a PDF showing this part of the schematic and layout with different zoom levels in case you can't download or open the Kicad project.
3- The manufacturer (TE Connectivity) suggest a 3 element matching network (as pictured in the datasheet) to compensate for the final mounting conditions (plastic case). I've implemented what they suggest, leaving the pads unpopulated. I tried soldering only a series inductor. I used SimSmith software to simulate the required value.
4- For all the tests you've requested me, I've populated the series element with a 0 ohm resistor.
5- I'm in the process of modifying the schematic and layout. As a real amateur, I mixed up the transceiver pinout with a different model. When I came to fully assemble one of the boards, I realized it would have never worked.
The schematic I attached is the modified version I'm working on. I haven't moved the antenna or modified the ground plane dimension nor its shape. only the position of the LoRa module and the transmission line shape.
6- WOW ! Huge findings tonight ! I moved the ferrite decoupled coax AFTER the matching circuit, right at the antenna. Look at the pdf I have attached. The results are in the last 4 pages.
Essentially, Even with the PCB mounted in its case, the VSWR stays relatively acceptable under all across the full ISM bandwidth from 902 to 928. The response is more flat and "clean".
This suggests me there is something wrong with the transmission line in the section where there is a ground plane.
Thank you so much once again for all your dedication helping me
Nicolas
