PN7160 harmonic issue

[Mardin]

Dear NXP

We are using PN7160 be our NFC reader solution, 

Now we faced EMI issue, following is actual PCBA and harmonic on spectrum analyzer,

We have tried some matrix of LC filter, but the conducted harmonics still very high,

Can someone give me directions or suggestions to debug the issue,

Thanks ...

BR.

影像 (3).png

 Image (14).jpegEMI chamber.jpg

[Tomas_Parizek]

Hello @Mardin , 

Can you share more details on how you measure the conducted emissions ? Do you measure somewhere on the power supply line? 

-> Where is the Spectrum Analyzer connected ? 

-> Can you share the original impedance matching measurement with the default LC filter, please? 

-> When you changed LC filter value, did you also change the remaining matching components to keep the same matching impedance? 

[Mardin]

Thank you Kaili

Actually we have tried backoff the power but still no abviously improvement,

I found our layout of Tx route is different with NXP, 

Our both Tx route all on the TOP layer but reference design is TOP and inner layer 3,

Following is the screensoot of PN7160 reference, 

Could you confirm the route may caused the harmonic issue or not?

Thanks again ...

gtX.JPG

 

[KaiLi]

Hello @Mardin 

The layout and routing of a PCB will definitely affect EMI/EMC, but EMI/EMC issues are not necessarily caused by the layout and routing of the PCB. So, merely judging from the routing cannot determine that the issues you are currently encountering are caused by the layout.

So do you want to improve EMC /EMI by adjusting the PCB layout and routing?

[Mardin]

Hi Kaili

Just compare the difference between reference board and ours, our both Tx wires all on top layer but reference board not, just courious if we change the layout and same with reference will improve the EMI harmonic issue or not?

BR.

[KaiLi]

Hello @Mardin 

could you share the pcb layout file with us and let us review it and to see if harmonic issue caused by Layout? if possible, please send it to us via email.

[KaiLi]

Hello @Mardin 

Please check section 9 of AN12988 (PN7160 hardware design guide) , which would be helpful for your issue.

[Mardin]

Thank you Kaili
Definitely, we have reviewed all PN7160 documents and included the harware design guide as well, our EMI LC filter be placed close to the PN7160 but the conducted emission still huge ...

[KaiLi]

Hello @Mardin 

Okay, understood. Another way to improve it may be to enable DPC and use the smaller target current to calibrate DPC, which can reduce the power of the transmitted RF signal.