nrf52833 RF channel center frequency shift in BLE mode

[jaeheung]

Hi.

Development platform : nRF52833-DK, s113, SDK 16.0.0, IAR 8.31.1

I am in the process of RF certification.

I downloaded the example at "nRF5_SDK_16.0.0_98a08e2\examples\dtm\direct_test_mode" directory.
Use the Direct-Test-Mode program of nRF-Connect-v3.4.1.

A problem occurred in which the center frequency was moved outside the margin of error as shown in the figure below.

What should I do to fix this?

[Andreas]

Hi,

 

Most likely this is caused by your 32 MHz accuracy, the RF carrier accuracy depends on that. Have you tuned the crystal in your board? This is done by replacing the tuning caps (shunt to ground on the XC1 and XC2 pins), too high carrier frequency means the caps are too small, you should increase them a E12 size or three. Try it out and see how the 'Transmit frequency error' changes, or the accuracy of an unmodulated carrier (you can use the radio test example in the SDK for this).

 

Best regards,

Andreas

[jaeheung]

Thank.

I changed caps for crystal.

I fixed it..