Hello, I’m curious about the reason why capacitor C13 is not assembled on the IMP005 Dev Board. I’m planning to recreate the schematic and am wondering why this capacitor is not used, as it seems like it would alter the characteristic impedance of the antenna.
Interesting… Although likely either assembly or shipping fault, the DevKit is not expected to be comply to a radio certification. So for the actual product, I would recommend you to have a look to the most current documents at Murata (I can see a DXF antenna file was there): Type 1GC - LBWA1UZ1GC | Wi-Fi® Modules / Wi-Fi® + Bluetooth® Modules | Murata Manufacturing Co., Ltd.
And also if you follow that recommended antenna design closely, you will benefit from modular certification which has been done to the module and antenna: Regional imp RF Certification References | Dev Center
In here you could find a design guide for various sub-system of imp005: Design Hardware With The imp005 | Dev Center