I am planning on using a Johanson 2450AT18A100E antenna for a portable design. I see that you suggest output matching to go to 50 Ohms, and Johanson suggests an input matching to go to 50 Ohms. Can you suggest a matching to connect the two parts? Do you have a similar chip antenna design with matching I can use?
Thank you.
John Nicosia
Hi John
You're using an nRF5340 in your design, correct? The Johanson antennas are popular chip antennas in nRF designs and are perfectly fine to use. You can check out the reference circuitry for our different package variants in the nRF5340 product specification here. They all suggest a Pi-network for matching from the ANT pin to the antenna you'll be using. Then depending on your design you can tweak the values of the capacitors and inductor to reach an impedance of 50Ω. Here's a snippet of said pi-network:
We also have an application note for circuit board guidelines available here that you might find useful.
Best regards,
Simon
Hi Simon, Thank you for your quick response. I am using the nRF5340 in a WLCSP package, and a Johanson 2450AT18A100E antenna.
What confuses me is that you add a Pi network on your output (to match to an antenna?), and Johanson puts a Pi network on their input (to match to 50 Ohms?), and they are different. Is your pin output 50 Ohms? If so it would seem that using the Johanson Pi, shown below, should be used? So I am confused.
You DK demo board uses what you suggest to match to an antenna, any antenna?
I will change the layout to what you suggest. Do you have any data on specific values for your device and this antenna?
Thanks again for your help.
Regards,
John Nicosia
Hi Simon, Thank you for your quick response. I am using the nRF5340 in a WLCSP package, and a Johanson 2450AT18A100E antenna.
What confuses me is that you add a Pi network on your output (to match to an antenna?), and Johanson puts a Pi network on their input (to match to 50 Ohms?), and they are different. Is your pin output 50 Ohms? If so it would seem that using the Johanson Pi, shown below, should be used? So I am confused.
You DK demo board uses what you suggest to match to an antenna, any antenna?
I will change the layout to what you suggest. Do you have any data on specific values for your device and this antenna?
Thanks again for your help.
Regards,
John Nicosia
Hi again John
For the WLCSP package, the recommended matching network is as follows, and in our experience, the RF after this network will be close to 50Ω in most designs, but we strongly recommend doing RF tests with different values to make sure the output is 50Ω.
The antennas also often have input matching networks that should be added as well, so there are usually two matching networks in many designs. You might also be able to make do with just one, but only testing will find out of this.
Best regards,
Simon
