PCB Antenna for BLE

[Alan Ajit]

Dear Nordic,

I am started design PCB antenna for BLE (nRF 52840).

can i use the same 2.4 Ghz Wifi PCB antenna for BLE circuit designing?

Is there any modification i need to do?

I need an immediate reply for starting my designing please help me 

[Andreas]

Hi,

 

Yes, any 2.4 GHz antenna can be used. Just keep in mind that even if you replicate the antenna exactly it might require slightly different matching or tuning due to differences in ground plane and/or enclosure. If you are in doubt about your design please feel free to upload it here for a free review.

 

Best regards,

Andreas

[Alan Ajit]

Hii..

In the nordic 52840 usb dongle i found that only one RF feed point is provided.but as per our previous designs we have RF feedpoint and Gnd.

does it matter in the performance...?

[Alan Ajit]

Hii...

i have one more doubt.. we have RF track of 55 ohms impedance and track length of 400mils.

1.can i use the same circuit..?

2.is it compulsory to add 0R matching circuit as per dongle we don't have enough space to place

  components so we just removed that circuit.Is it make any difference in performance..? 

Best regards

Alan

[Andreas]

Hi,

 

Do you mean feed point on the antenna? Some antennas have one feed as the only connection, some (inverted-F style) has a ground short pin. Both are fine, just make sure you replicate all of a given antenna, and not make a mix of two or something.

 

Best regards,

Andreas

[Andreas]

Hi,

 

55 ohm is quite close to 50 ohms, so it will not cause an awful lot of loss. The antenna, once tuned, will work just fine with this.

Per the dongle design, R1 = 0ohm and C25 = NC are added in case they are needed for tuning the antenna, this is not known when the board is laid out. Once the tuning components are determined, the layout is not changed to remove the ones that are not needed. 0 Ohm is needed to short the signal towards the antenna.

In other words, the 0 ohm itself is not needed, but you should reserve the space in case you need to populate an inductor or capacitor here. If that is needed for tuning the antenna, but not populated due to space restrictions or something, range performance will suffer.

 

You can find our whitepaper on antenna tuning here.

 

Best regards,

Andreas