FCC/CE RF Certification Fail

[Elliott]

Hi,

We are using the Nordic Semi nRF51822-QFAA-T to do BLE project, but when we test CE/FCC RF test(Conducted / Radiated), there has a lot of noise around 2.4G.

BTW, I used Nordic Studio DTM to test it.

Nordic Studio DTM setting

Test result shows below:

backup image

schematic

PCB layout

Could anyone help me please?

Elliott

[Elliott]

Hi Kristin

I have to test it in RF lab, but the signal waveform would be the same when I turn on the peak hold/Max Hold, right?

How can I control the PA turn on/off?

Thanks,

Elliott

[FormerMember]

The PA is automatically turned on when the radio is transmitting, and off when it is not transmitting anymore. It cannot be controlled by a user.

During the ramp-up of the PA there will be some transients. However, they will only be there for a very short amount of time, and before modulation has been turned on. By using "peak hold", you can see the envelope over time. The spectrum will look a little wider than what it actually is because of the transients. However, since the transients occur before modulation has been turned on, it is ok. Reducing the resolution bandwidth in the spectrum analyzer (if possible) will make the transients less visible.

[Elliott]

Hi Kristin

I found a new part of match balun, BALF-NRF01D3 ( not BAL-NRF01D3), do you know which part is suitable for nRF51822 ? There have a lots difference in RF performance, for example, BALF-NRF01D3 Return loss = 17dB, but BAL-NRF01D3 Return loss=10dB.

Could I solve this problem by changing match balun?

Elliott

[FormerMember]

Hi Elliot,

I have updated my answer regarding the baluns, please have a look at it.

Kristin