nRF52810 DEMO design signal is poor

[ArchieL]

Sometimes the DEMO cannot be searched by mobile phone, so I suspect it may be the problem of antenna resistance matching.

[Andreas]

Hi,

 

It's a bit hard to see from this image alone, but the designdoes not look ideal. As you are saying it is only sometimes it's not possible to scan the demo it should indicate poor RF design, you should then be able to more consistendly scan it if you place it right next to the phone.

Main issues:

1. The antenna is mounted (partially) above the battery, which will prevent it from radiating and detune it.
2. The buzzer is placed partially inside the antenna keepout, which will also prevent it from radiating properly.
3. The antenna does not look like it has been tuned/matched, there is only one component (C15) and that is NC in the schematic.
4. C7 shall be 100pF, not 12 pF.

 

It could also be related to the 32 MHz crystal loading, C1 and C2 should be C1 = C2 = 2*CL - 4pF, CL is specified for your crystal part. I do not expect this to be the cause as the crystal is likely not inaccurate enough, and this would most likely prevent the device from being scanned at all.

 

Best regards,
Andreas

[ArchieL]

Thank you for your analysis. I will refer to it and conduct the revision test.