nrf21540 general dbm/antenna question

[Jenwhiz]

We are testing four nrf21540dk boards with the onboard antenna, +3dbm, and +5dbm external antennas.

The onboard antennas and the +3dbm external antennas preform similarly (RSSI data). The +5dbm seems to preform better than both the onboard and the +3dbm external antenna.

The fact that the +5dbm antenna provides better performance tells me that my setup is correct for testing, but I was surprised that the +3dbm antenna didn't perform better than the onboard antennas. Is this because the onboard antennas also supply about a +3dbm gain? If that is the case is that documented anywhere? I could not find that specification online.

I am looking for verification that my results are in line with what you would expect to see or if I am missing something.

[Didrik Rokhaug]

Hi,

Because of a public holiday in Norway we are short on staff today, and we will therefore have to get back to you next week.

We apologize for the inconvenience.

Best regards,

Didrik

[Kenneth]

Hello,

Antennas are passive components, so they don't really add gain per se. It simply means that the antenna radiates power in some directions better than others, so if it's +3 or +5 dB, then that means it's equally less in other directions, compared for instance to an ideal omnidirectional antenna that radiate the same in all directions. If you want more detailed information please search for what is antenna gain on the web. But to answer your question about the PCB antenna, it likely radiates power in some directions better than others, just like external antenna, though likely an external antenna have better control over which direction it radiates better.

Best regards,
Kenneth