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Antenna

Guys I am planning on a using the linked antenna on an arduino proto board with 868 data radio and bluetooth chip. I just want to confirm, is it as simple as following the recommended layout and ground plane of the antenna and feeding the same antenna with the two different RF chips in alternative times. is an RF switch or special circuitry required ? any suggestions is welcome

thank you

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  • \$\begingroup\$ Why wouldn't you simply use two of them? \$\endgroup\$ – Dave Tweed Feb 8 '18 at 18:58
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Unfortunately it's a little more complicated than that. Notice on the datasheet that each frequency has a little schematic showing the required matching circuit: enter image description here

This antenna is not a broadband matched antenna - it will only work well at the single frequency that you use the matching circuit for. So you can get it to work EITHER at 868MHz or at 2.4GHz, but not both simultaneously.

You may want to consider a true broadband antenna instead, such as PA.710.A.

Now, consider how you are going to connect the antenna to the two chips. You could just connect the RF trace from the antenna to both chips, but you will get unpredictable mismatch because you don't know what the impedance is of the other chip when it's not being used. Will it work to some extent - yes. But I would not recommend it. The better way to do it is to connect them using either a SPDT switch or a diplexer (maybe DPX202700DT-4035B5). Personally I would use the diplexer, because you won't need a switch control line and because it will let you use both chips simultaneously.

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  • \$\begingroup\$ Thank you for the answer! unfortunately I am constrained on space pcb 20x30mm and have MCU and GPS to also add. I like thhe diplexer idea but would need to find a different antenna to the one linked as its length is an issues \$\endgroup\$ – Rustie0125 Feb 9 '18 at 4:18
  • \$\begingroup\$ If you're not able to find a broadband antenna that fits, using two antennas (with different matching circuits) is a pretty good option. \$\endgroup\$ – Selvek Feb 9 '18 at 5:30

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