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I'm designing a PCB which uses the ESP32-D0WDQ6 WiFi chip (not the entire module!). I want to add the uFL connector so that I can connect an antenna instead of using the PCB trace antenna.

Now, I searched for this before and found this in a datasheet of SIM9000 which is related to designing a 3G module which an antenna connector:

2 layer example

This shows the recommended layout for the 3G module's antenna feed line on a 2 layer board.

My question is, can I use the same idea with my ESP32 chip on a 4 layer board? (I have inner layers dedicated to ground and power plane each)

More specifically, is it needed that the inner copper pours (ground and power planes on inner layers) be left under the antenna feed line and the uFL connector itself or do I have to remove them?

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  • \$\begingroup\$ Keep the ground under the RF trace. You can use the same guidelines as for the 2 layer board. But you need to recalculate the the trace width and ground clearance for your 4 layer stackup. You can use the power place as the reference for the RF return current, but I would avoid it. \$\endgroup\$ – Mike Dec 9 '17 at 19:25
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You can use the same coplanar waveguide. You'll want to get Saturn PCB Toolkit to calculate the appropriate geometry for the shorter distance to the inner ground plane. You would be best served to keep this trace on the same outer layer, and keep a solid ground plane under it.

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  • \$\begingroup\$ As far as I remember Saturn PCB TOolkit doesn't do Grounded Coplanar Wave Guides, which is the transmission line topology shown. Perhaps it's better to use some online calculator for that. \$\endgroup\$ – Mike Dec 9 '17 at 19:38
  • \$\begingroup\$ @Mike Not sure how far back that was, but it's been a feature for at least the last several versions. \$\endgroup\$ – Matt Young Dec 9 '17 at 19:46
  • \$\begingroup\$ Thank you for your answer, I will calculate and adjust the trace width to match the 50ohm impedance today. I just have two more questions. 1. Would this design be alright? i.imgur.com/HTFzmUT.png 2. On the image on the top left, you can see the soldering pad for a triac (part of a crowbar circuit), that is its GND pad, is it alright if I extend the top ground pour of the feed line "shield" onto it as well or should I connect it to ground separately using vias? \$\endgroup\$ – caffeine93 Dec 10 '17 at 12:31

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