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Hi all,
I have a question about the PCB layout of BCM20737S, since it uses an embedded antenna, we have to make sure our layout won't affect its RF performance.
I have read the layout suggestions in BCM20737S datasheet and the reference design.
Questions:
There is a L-shaped ground around the BCM20737S chip, in datasheet it says this L-shaped ground is required for the embedded BLE antenna, and we need to keep GND continuous. My question is: should we connect this L-shaped ground to the GND pins of BCM20737S chip? Or should we just place the L-shaped ground close to the chip but not connect to any pin?
Thanks
Jingdong
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You should connect the L-shape ground to your system/motherboard ground. Although it is electrically the same, it is not a good idea to connect it to the pins of the module directly.
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Hi boont,
I know the longer arm of the L-shaped GND should be connected to system ground of the board.
How about the shorter arm of the L-shaped GND? From the reference design, the shorter arm is not connecting to anything, just floating there in to the module a little bit.
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I couldn't recall what is this. Which layer is it on? But it appears that it is a little electrically short to be of any significance.
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From the reference design, this L-shaped GND is on L02_GND layer instead of the top layer. I think the L02_GND layer is the second inner ground layer of the whole four-layer PCB stack.
I am just not sure why the shorted arm is there, without connecting to anything. I think the L-shaped GND is not electrically small for a 2.4GHz signal.
Is it OK to use the third layer as ground plane layer and put L-shaped GND on that third layer? I don't know how this L-shaped GND can enhance RF performance of the embedded antenna so I am not sure about any modification I made during layout.
From the post you give to me, I still cannot see what does the shorter arm connect to. Maybe it is just floating.
From the post below, I can also see the L-shaped GND in first figure.
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I still couldn't figure out what is that little short arm you have circled out. I have attached the above layout with the vias turn on. Hope it helps.
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Hi boont,
It looks like the short arm is connected to ground through the via.
Is it possible for you to send this layout file to me? I am a student at Missouri University so it won't be used for any commercial business. Since manufacturing the PCB will cost a lot of money for us student, I just don't want to make a mistake in layout.
It is OK to send just the local region of BCM20737S to me, because that is the only part I didn't understand. My email is sunjing@mst.edu.
Thanks
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