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CC3220MODA: RF Layout Recommendations, any additional keepouts?

Wataru Nishizawa1
Prodigy 60 points
Part Number: CC3220MODA

Is there any guidance available for the CC3220MODA (with an Integral Antenna) keepout? I see 1mm overhang of the module from the edge of a PCB and 6mm keepout of metal based on the CC3220MODA datasheet, 7.3.3 CC3220MODAx RF Recommendations. I wanted to know whether or not any keepouts from the overhanging edge of the CC3220MODA against plastic (such as enclosures) and metal (such as screws) are necessary. I appreciate it if you would provide me with keepouts for both materials (plastic and metal) if they are needed and different.

Thank you.

  • 0
    Guru 39650 points
    Hi,

    Device enclosure always affects antenna performance, especially if is located in reactive near field (~0.159 * wavelength). Plastic enclosure may to affect antenna performance as well (depends on type of plastic). Best practice is to do own measurement inside enclosure.

    Nice video about antennas training.ti.com/importance-antenna-design-optimized-range-performance

    Jan
  • 0 in reply to Hnz
    Prodigy 60 points
    Hi,
    Thanks for your response.
    We are in the design phase now, so we wanted to get an idea of keepouts for other surroundings than the PCB we need to consider. The datasheet specifies keepouts against metal on the PCB as well as PCB layout (overhang), so I was wondering if there is any guidance for keepouts against surrounding objects off the PCB, to help us design our enclosures/mechanical parts correctly (or so that they don't hurt Wi-Fi performance of the CC3220 module). That was the intent of my original question. We will definitely do our own measurement once we get our PCBA back and mechanical parts for our enclosures.
    Thanks again.
  • 0 in reply to Wataru Nishizawa1
    Guru 39650 points

    Hi,

    It is hard to give you any general guidance because it is so related to each design. Maybe you can wait for answer from TI side.

    I can give you a few advices. At 2.4GHz is reactive near field approximately 2cm from antenna. Any object in this distance from antenna will affect antenna performance. Some objects will affect performance negligibly but some objects significantly. Metal objects in this distance could load antenna significantly. And for this reason is good idea do not have metal object in this distance. But plastic housing may affect antenna as well.
    And here could be a small issue to use module with integrated antenna (like a C3320MODA). At this module is not available pi matching circuits.That means you cannot properly compensate antenna mismatch which may to be caused by your device and enclosure design. In some designs may to more efficient use module without antenna and your own PCB or SMD antenna. But all is about device construction...

    Jan

  • 0 in reply to Hnz
    Prodigy 60 points
    Thanks again. I got very curious why the datasheet says the module needs to have an overhang of 1mm from the edge of a PCB but no mention on other surroundings such as enclosures.
    I will wait what TI people say.
  • 0 in reply to Wataru Nishizawa1
    Guru 79905 points

    Hi,

    Datasheet contains specific requirements related to usage of CC3220 module only. It is not possible cover all general recommendation and good practises related to end product design in datasheet. This is similar like a PCB design. There is a many recommendation and good practices how to design PCB. But at the end it is about experiences with such kind of PCB design.

    But wait for answer from TI. Maybe they will give you some additional resources.

    Jan

  • 0 in reply to Jan D
    TI__Mastermind 46291 points

    Wataru,

    The best practice is to keep any metal away from the antenna and to use plastic housing. 

    From our experiments with teflon (permittivity = 2.1), we found that the S-parameter and radiation pattern were not affected with the following specs:

    1) H1 = main baord PCB bottom to plastic housing distance, H1 >= 3mm

    2) H2 = module PCB top to plastic housing distance, H2 >=3mm

    3) H3 = module PCB side to plastic housing distance, H3 >= 5mm

    Hope this helps,

    Seong