Using nRF51822-CFAC + BAL-NRF02D3 with flex PCB (FPC) trace antenna?

[Brian]

Hi,

I'm designing a four layer flex PCB with the nRF51822-CFAC and recommended ST BAL-NRF02D3 balun and PCB trace antenna (not chip). I have a couple of questions.

• Can I use the recommended design files (nRF51822 webpage --> "downloads" --> "reference layout") and guidelines here to tune the antenna still? Do you suspect that the design files are close enough? Has anyone designed a flex PCB with these parts yet?
• Should I add one or two shunt components to the antenna for better tuning, since my design is further off of the recommended stackup?

Thank you for your time, Brian

[Øyvind Karlsen]

Hi Brian,

You can(and should) definitely use the reference layout as well as the general PCB design guidelines. Remember to add a matching network between your balun and the antenna. With a flex PCB you will probably see some weird effects, but you will have a functional circuit as long as you stick to the reference layout, and do your tuning well.

You should be fine using only one shunt component since you are using a PCB antenna you will be able to do a lot of your tuning by cutting the antenna to size. The idea is to cut the antenna until you reach G=1 circle then add a shunt capacitor to pull it in towards 50ohm.

Best regards,

Øyvind

[Brian]

Hi Øyvind,

Thank you so much for your helpful reply! The devzone site is very helpful.

Brian