I didn't really know where to ask this question but since it is related to a module I need to use for a project with ZigBee I will ask it here.
The GND requirements for the EFR32MG21 Series 2 Modules that can be read in p.33 of the datasheet are not acceptable for me. It says that a size of 50mm is required for optimum antenna efficiency but that is too much. My device can't exceed 20mm total.
So, I was thinking about using a dipole antenna like the Molex 1461530050 but I'm not sure if I still have to meet the GND requirement. I ask because the dipole antenna doesn't require the GND but since the chip antenna is still there, I'm not sure.
Is the module going to use both? Or will it somehow "switch" to the external antenna?
The recommended ground plane width of 50mm and the module placement guidelines are only applicable if the on-board chip antenna is used, so they are not required in your case if you choose to use the external dipole antenna.
No, the module will not use both antennas. The module's RF path (using internal or external antenna) is configured in the EmberZNet stack for Zigbee, which is detailed in this KBA -> https://www.silabs.com/community/wireless/zigbee-and-thread/knowledge-base.entry.html/2020/05/21/switching_antennapathonseries2devicesefr32m-soxd.
Awesome! Thanks for the confirmation and the link! Very useful!
For what is worth, according to the link you sent and the code itself, the default antenna is in fact the external U.FL antenna. That would explain the poor distance I was getting without it (about 80 ft) and the awesome range I got once I connected an external antenna (350ft).