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RF Circuit for a Custom MKW41Z board, SMD antenna

Question asked by David Karibe on Oct 4, 2018
Latest reply on Oct 8, 2018 by David Karibe

I am designing a compact custom BLE board with the MKW41Z controller for wearable application. I have some recommendations from the antenna datasheet on the RF matching circuit and also the 50 Ohm transmission line impedance matching from the NXP FRDM-KW41Z schematic. Recommended 50 Ohm controlled impedance matching

Recommended matching network for Molex 2.4Ghz MID SMT antenna

Of course I have replaced the "J5 and ANT1" part of the circuit from the FRDM-KW41Z schematic with the Molex MID SMT antenna [with its recommended 1.3pF and 1.8nH RF matching circuit].

 

Custom matching circuit

And routed the PCB as close as possible to the recommended working layout in the application notes:

Critical custom PCB layout

3D view of PCB routing

 

My problem is I cannot figure out a specific trace width to use on the RF trace from the MCU ANT pad to the antenna

 

If I was to pick a PCB manufacturer who makes PCBs using FR4 boards of a specific dielectric constant, board thickness and top copper thickness, like OSHPark 2oz Copper with 0.8mm FR4, how do I figure out the width of the trace required and distance between the trace and the top ground plane. I need to fix this final part in order to do via stitching and make prototypes. Any assistance will be greatly appreciated.

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