RE: nRF52840 BLE Antenna Simulating Issue

Radio — Tue, 11 Aug 2020 11:24:15 GMT

Hi Vincent,

As Andreas mentioned, what you are simulating is a CPW trace impedance. But if you really want to obtain the antenna S11, you can try simulating it using an EMV simulator. But you should try to simulate the antenna including your ground as closer to the actual design as possible. This is because, actual ground affects the antenna performance. Please see the thread below.

https://devzone.nordicsemi.com/f/nordic-q-a/64467/nrf52840-dongle-antenna-simulation-in-cst

However, in your case you don't have to do a simulation as mentioned by Andreas. You can use the reference design. But you may have to tune your antenna because manufacturing/substrate/component conditions might vary.

Hope this helps.

Thanks!

RE: nRF52840 BLE Antenna Simulating Issue

Andreas — Fri, 06 Mar 2020 07:39:29 GMT

Hi Vincent,

This is a calculator for a coplanar waveguide (which is a transmission line), not a monopole antenna. The impedance you are calculating is the characteristic impedance of the line, not the antenna load impedance which the nRF52840 PS describes.

Although not accurate, you could probably get a ballpark impedance model with this. Assume an open and capacitive load at the end of the line, then add your 200 ohm transmission line (quarter wave trasformer), you will end up somewhere near the constant reactance = 1 circle. The load cap will then bring you to 50 Ohm:

Anyway you are not supposed to worry about calculating or simulating this when following the whitepaper, it will work just fine without, as long as you follow the instructions.

Best regards,

Andreas