RE: Problem with Texas swra117d PCB antenna

thpuch — Sun, 09 Jun 2019 20:50:43 GMT

Hello,

thank you for your fast reply.

Attached is the complete design.

I am using the following crystal:

ABM3-32.000MHZ-B4Y-T
CC4V-T1A-32.768kHz-12.5pF-10PPM-TA-QC

If I change the capacity from 12pF to 18pF, for the 32MHz, then it works fine.

Thank you for the hint!

Best regards

Thomas

RE: Problem with Texas swra117d PCB antenna

Andreas — Thu, 06 Jun 2019 08:47:03 GMT

Hi,

The layout has some deviations compared to our reference design, so the component values are probably not optimal. You should still see the signal (and you do), just lower signal strength. Also, you only have 1 component for matching the antenna, which might not be enough and it is not mounted anyway, this will potentially further reduce signal strength.

Seeing radio transmission at a higher frequency than expected might indicate too high crystal oscillator frequency. This is often the case if you have too small load caps on your 32MHz crystal (lower capacitance -> higher frequency). The small section I am able to see from your image does not really make sense, could you share the rest of the NRF52840 design as well or at least the 32 MHz crystal part? Also if possible the crystal part number you are using.

Best regards,

Andreas