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Consideration when designing RF PCB for FCC/CE tests

a7med7usam

Hi,

 

I hope anyone who has experience designing RF PCBs which has passed FCC or CE tests can help me. I am designing a couple of PCBs currently that is all required to pass the FCC or CE tests. Here is the details of the design:-

 

1) 6 layer PCB design.

2) 40 mm x 40 mm size

3) Include three chip antennas: one for GPS, one for GSM, and a shared one for WIFI and Bluetooth.

 

As you can see, this will be used for tracking and sending/receiving data over all available communications like WIFI and Bluetooth. My questions are:

1) What should I consider when designing such PCB please? like ground and power planes, isolation, impedance ....etc.

2) What is the suitable PCB material for this type? currently i have planed to use  the 370HR material, is it good enough ?

3) I have contacted the manufacturer to control the impedance of the three antenna tracks to be 50 Ohm, is there anything else the manufacturer should know/do ?

4) For such design, do I need to consider the dielectrinc of the PCB material and signal loss ?

5) What would be the FCC tests exactly? what is needed in the design to pass this test please ?

 

any help or discussion is much appreciated!

 

Thank you,

Ahmed

  • 0

    This is a very complex topic.

     

    At GHz frequencies everything matters and it's impossible to know what matters less or more in your case without knowing the particular details. For example, if you only have 3, very short microstrips feeding the antennas from one or more ICs, then a lot of things become less important than if you had a complex RF system with a lot of transmission lines, while other things remain essential regardless of what you're trying to do, like grounding - at these frequencies a simple solid ground plane does not suffice.

     

    About FCC and CE, they both require EMC testing and you will have to design your entire product with this in mind and probably invest in some equipment for pre-compliance testing.

  • 0 in reply to jadew

    Thank you for your help.

    The tracks which are feeding the antennas are short and directly go to filter then the antenna. It's not complex network I think. But I am wondering what should I check first to know if this design is good? Can you please tell me what cautions i need to take before any testing ? and what cautions to take for the device to pass the EMC testing please ? Are there any labs that can help in testing before applying for FCC or CE please ? It would be great if you have any sources/Books/Links for reading about the steps I need to take please.

  • 0 in reply to a7med7usam

    As with all other devices, the most important thing to watch out for is long, high current paths, but in this case, since it's an actual RF device, you also have to make sure that none of the tones used to generate the needed signals are escaping from your device, either directly or worse, leaking in the amplification stages and getting radiated with the help of the antennas.

     

    You can do in-house pre-compliance testing yourself, with the aid of a SA, a few home-made probes and a few other tools that you can buy or build yourself, but there are labs that can help you with this too. They will test it for you and tell you what the issues are and more importantly give you suggestions on how to fix them (depends on where you live I guess, personally, I don't know any).

     

    About books, I suggest Electromagnetic Compatibility Engineering by Henry W. Ott.

     

    You might also find this useful: https://www.youtube.com/watch?v=uLIr1eFjY2s