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I'm integrating an nRF24L01+ chip into a PCB I'm designing, but I'm a little confused about the best PCB antenna design. In the datasheet for the chip, they specify an antenna like this:

nRF24L01 recommended antenna

However, all of the boards you can buy with this chip use a different design:

nRF2401 board

The design is quite different. Not only is it a different shape, it also has that extra stub track with a via.

What is the reason they do this? Is it a more effective antenna, or does it just take up less PCB space?

If it is a superior design, how can I create my own? Do I just draw a wiggly line that looks roughly similar, or do I have to get the dimensions precise for it to work properly?

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    \$\begingroup\$ I did some testing with nRF's lately (the one below, with small PCB antenna), and the orientation and vicinity of other metalic elements is quite important. \$\endgroup\$ – Michel Keijzers Aug 8 '17 at 22:07
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What is the reason they do this? Is it a more effective antenna, or does it just take up less PCB space?

Both?

The meandered part is probably an inductive element, increasing the electrical length, and the stub might match the impedance. Looks a bit like an inverted-F antenna.

In fact, it's a meandered inverted F in PCB shape. Probably, you'd call it a MIFA

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"If it is a superior design, how can I create my own? Do I just draw a wiggly line that looks roughly similar, or do I have to get the dimensions precise for it to work properly?"

Antenna design is not going be easy. Here is a link on how I would design an antenna.

http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-design/

You neeed to remember this, tune the antenna inside a case as a finish good with a complete assembly. Tuning it bare PCBA won't be accurate, once the antenna is in close proximity with other stuff surrounding it; the frequency will shift away slightly.

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