RF feeding line LCL values

[Bougrine Anis]

Hello everyone,

Currently I'm working on a specific BLE project so I have to design my own PCB, but basically I'm en embedded software engineer so I don't have deep knowledge when it come to PCB design. Therefore, I decided to opt to Nordic PCB design recommandation which is included in every chip product link. For example regarding the nRF52833 reference manual we can see that the RF feeding line LCL values are:

However, when Nordic team designed the development board for the same chip, they used different configuration for RF feeding line (you can get this by downloading the PCB desing of nRF52833 DK):

Here I've become confused since on one hand Nordic recommend to stick to the reference manuel settings and on the other hand Nordic team uses different configurations for the same chip.

And if the answer to this is "LCL circuit is antenna dependant", I would say that in the first example taken from the reference manuel there is no antenna so why would they specify specific values for the LCL circuit if there i no antenna ?

Please don't hesitate to share with me your knowledge about this topic, any information would be beneficial.

Thank you. 

BR,

Bougrine Anis

[Jared]

Hi there,

For example regarding the nRF52833 reference manual we can see that the RF feeding line LCL values are:

This is the reference design for a nRF52833 CJAA WLCSP package,

However, when Nordic team designed the development board for the same chip, they used different configuration for RF feeding line (you can get this by downloading the PCB desing of nRF52833 DK):

While the development kit are using a nRF52833 QFN package.

CSP and QFN are very different chip packages and therefore have a different reference design. If you check the reference design for the QFN package then you'll see that development kit does indeed follow it.

Lastly, designing a hardware layout especially for RF products is no easy task, for beginners I would always suggest starting out with a pre certified module that already have the RF part implemented. That would make it very easy to integrate the module into your design,

best regards
Jared 

[Bougrine Anis]

Thank you for your fast reply, I admit the RF PCB design is complicated due to its environment dependencies that requires specific tuning which is costly. Opting for pre-developed PCB chips is a good idea as a first product version than we can work on cost optimisation.

Thank you another time for the providing link.

[Jared]

Hi,

We offer a free tuning service once your design has been reviewed and verified by us. But I would still encourage you to start with a module if it's your first time designing a RF product,

regards

Jared