Using pre-certified FCC module does not dispense you from the require certification. You can only reuse the intention emission test results. You are required to FCC/CE certify the product as a whole no matter the component inside is certified or not. The certification of the module is valid for you only if you use it as it without any addition circuitry. So pre-certify module is more or less for marketing purpose.
RF design is IMHO a black art, which is best left to the professionals, hence I dont touch it.
However Nordic provide reference designs at PCB level, which somewhat mitigate this problem.
I use another option, which is to contract a Chinese company who specialise in BLE and RF, to customise an exiting, tried and tested design, to add the functionality I require for a specific product.
The product still then needs to be tested and certified, but as the RF end of the PCB is the same as other boards which have passed certification, there is normally not an issue with getting the customised board certified
RF design is IMHO a black art, which is best left to the professionals, hence I dont touch it.
However Nordic provide reference designs at PCB level, which somewhat mitigate this problem.
I use another option, which is to contract a Chinese company who specialise in BLE and RF, to customise an exiting, tried and tested design, to add the functionality I require for a specific product.
The product still then needs to be tested and certified, but as the RF end of the PCB is the same as other boards which have passed certification, there is normally not an issue with getting the customised board certified
