QUESTION

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Reference circuit for EMC compliance
Dear Sir/Madame,

In a project where I'm using your model SR4L002 (Lucida) connected to a GPRS module (Quectel M95), I sent the PCB designed by me for the CE-RED and FCC certifications to a lab and all tests passed except RF Radiated Emissions which fails due to GPRS harmonics.

Analizing the circuit I realised that for the Inductor connected into pin 4 of the Lucida Antenna, by mistake, I mounted a 2.2nH inductor instead of the recommended value (15nH).

My question is if, from your point of view, you think that an unbalanced value in that inductor could be noisy enough to fail radiated emissions test (the test restriction is the lowest one as it's a general consumer product).

Thank you very much in advance

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1 Answer

answered by
Yes, it can fail due to the self resonant frequencies of the two components. The 15nH will tend to block unwanted harmonics whereas the 2.2nH will allow the harmonics to go from the PCB ground through the antenna and into the radio front end to be re-radiated.
commented by
Thank you very much for the answer. It's been very useful.
Best wishes.

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