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I am am new to RF design and I need to place a chip antenna due to space limitations. The only antenna that is easily available to me has a very weird layout.

There is no physical connection from the feedline to the antenna and also the dimensions of this gap are not clearly mentioned. Can anyone please explain what is going on in this layout?

The link of the datasheet.

Recommended PCB layout

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  • \$\begingroup\$ Welcome to EE.SE! "There is no physical connection from the feedline to the antenna". I'm confused by your statement. The feed appears to be connected to the right side of the chip antenna in this layout example. \$\endgroup\$
    – Daniel
    Commented Apr 15, 2019 at 16:58
  • \$\begingroup\$ Thank you @Daniel I am excited to be here and thank you for your reply. If you look at the upper image you will see that feedline goes vertically down and then there is a break. The antenna terminal on the right side is electrically connected to ground. I have never seen anything like this. Usually for chip antennas one side is NC and the other is connected directly to the feedline through a 50 Ohm line. \$\endgroup\$
    – Saad Saif
    Commented Apr 15, 2019 at 17:10
  • \$\begingroup\$ That does look strange. If the gap were important, I'd expect dimensions. The stub (the connection from feed and antenna to ground) has dimensions. That weird gap in the feedline is just ignored. \$\endgroup\$
    – JRE
    Commented Apr 15, 2019 at 20:52
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    \$\begingroup\$ I think you have just two choices: ask the manufacturer what they meant to say, or use an antenna with better documentation. \$\endgroup\$
    – JRE
    Commented Apr 15, 2019 at 21:01
  • \$\begingroup\$ @SaadSaif thanks, missed that! \$\endgroup\$
    – Daniel
    Commented Apr 16, 2019 at 17:21

1 Answer 1

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That is a filter. It's a stub filter. The length of the trace is tuned a multiple of the wavelength of interest an then shorted to the ground plane.

Stub Matching

stub image

They come in all shapes and sizes

enter image description here

Here are some that show the non-connected nature of some styles: http://home.sandiego.edu/~ekim/e194rfs01/filterek.pdf enter image description here

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  • \$\begingroup\$ Thank you for your response. Unfortunately the datasheet does not mention the dimensions of the gap so I cannot replicate it in my design. \$\endgroup\$
    – Saad Saif
    Commented Apr 17, 2019 at 9:32

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