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Is it feasible to use multiple (e.g. 2) independently transmitting antennas on the same PCB (e.g. 5cm x 5cm) operating in the same band (e.g. 2.4GHz), though on different "frequency channels"?

I'm not sure what the radiation pattern looks like for typical PCB or modular 2.4GHz antennas, but I am wanting to have a device receive a data stream on one antenna via a (fast) proprietary protocol, and interact with another device via BLE on the other antenna. Unfortunately the throughout needs are too high to use a single antenna with modern SoCs (e.g. from Nordic).

I was hoping if I was able to space the antennas out by about 5cm and orient them in opposite directions, then there would be minimal interference assuming different frequency channels were used.

Any explanation on why or why not this would work would be much appreciated. Thanks

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    \$\begingroup\$ You're thinking too much black/white, it is not a case of works or doesn't work. Of course the radiation patterns of the antennas will be influenced. How? Ask an antenna designer. Even if you have a proposal how to layout your antennas it might take such a designer a couple of weeks to come back with some numbers. Yes it is feasible but you will have to try and see what works better and what works not so well. \$\endgroup\$ – Bimpelrekkie Nov 28 '19 at 14:49
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    \$\begingroup\$ The most difficult thing will be handing the reception on the receiver of the signal from the transmitter. You will need very large dynamic range electronics before the receive detector. \$\endgroup\$ – user69795 Nov 28 '19 at 22:04
  • \$\begingroup\$ @user69795 Is that because two phase-shifting (due to different frequency) signals will result in constructive or destructive interference at different times? \$\endgroup\$ – abc Nov 29 '19 at 15:22
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    \$\begingroup\$ If the device is transmitting while another one is trying to receive, the transmitter will essentially overpower whatever signal you're receiving even if the frequency is slightly different. This is because the front end RF electronics will effectively be railed due to the high power. \$\endgroup\$ – MadHatter Nov 29 '19 at 20:41
  • \$\begingroup\$ You may want to look up “Wi-Fi Bluetooth coexistence”. The topic is as old as the technologies. In many cases to achieve the best performance you want to have both in the same chip, which in turn usually means the same antenna. I’m not sure using separate antennas actually helps. \$\endgroup\$ – jcaron Nov 29 '19 at 23:22
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I can tell that this can work like a charm: I once designed a (professional) PCB with ZigBee and BLE (both 2.4GHz) on the same board with chip antennas spaced only 3cm apart from each other and 90deg orientation.

I do not say that there is no influence from one to the other, I just say that I did not notice any performance degradation when running both simultaneously.

It might have to do with the facts that ZigBee is on a static channel and BLE is pseudo-hopping on multiple channels and both have different modulation schemes.

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  • \$\begingroup\$ Comparing Zigbee to “high throughput Wi-Fi” is probably an apples to oranges comparison. \$\endgroup\$ – jcaron Nov 29 '19 at 23:23

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