NRF52840 QFAA matching network

[julienh]

Hi,

We are designing a product with NRF52840 QFAA + GNSS. Due to size constraint, we are planning to use Ignion DUO mXTEND for both BLE and GNSS.

The antenna manufacturer can help with tuning but I'm not sure about the output of the NRF52840. When I look the different DK + thingy 91, I see different matching network topology.

On PCA10056, there is only a pi matching network plus a capacitor after RF connector.
On PCA20035 (thingy91) there is a more complex matching network with PA (SAFFB2...), ESD diode etc...
On PCA20035 (thingy52) there is another configuration.

The manufacturer recommend this configuration below but I don't know if I can put that directly on the output of the NRF52 or if I need to keep a pi filter at the ouput plus the filter that they recommend after the RF tunning connector ? 

Thank you

[JONATHAN LL]

Hi,

I need to keep a pi filter at the ouput plus the filter that they recommend

 Yes


So the recommendations we have in our schematic and reference design serve more than on purpose. We do it to match and to filter the harmonics, the harmonics is equally as important to filter. 
You can read more about it here https://infocenter.nordicsemi.com/topic/ps_nrf52840/ref_circuitry.html?cp=4_0_0_6_2_13#concept_hf5_hzm_fs 

Depending on the chip type there will be different topology's https://infocenter.nordicsemi.com/topic/ps_nrf52840/ref_circuitry.html?cp=4_0_0_6_2. 

Here is an example:


So the Z1, Z2 and Z3 here will be replaced with the recommendations you got from the antenna manufacturer.



We also do give feedback on HW and Schematic so when ever you have a draft ready then feel free to create a ticket called HW review (product name), you can do it as a private ticket. 

Regards,
Jonathan