RSSI Accuracy in dBm

RE: RSSI Accuracy in dBm

Marjeris Romero — Mon, 16 Mar 2020 14:08:44 GMT

Hi,

The receiver has it's own ADC, it has nothing to do with the SAADC peripheral. The accuracy of +-2dB is for the RSSI value.

Best regards,

Marjeris

RE: RSSI Accuracy in dBm

Thavish — Tue, 10 Mar 2020 10:49:04 GMT

Is there a physical explanation as to why the percentage accuracy is the same for both values? It seems strange that the internal radio doesn't have a fixed absolute accuracy instead.

RE: RSSI Accuracy in dBm

Thavish — Tue, 10 Mar 2020 10:08:52 GMT

Thanks, that's helpful. Can I check that I understand the RSSI measurement process right? After a signal is received by the antenna, it is passed to the SAADC, then to an IIR filter which outputs a value in dBm. The internal accuracy of the SAADC is ± 2 dB.

RE: RSSI Accuracy in dBm

Marjeris Romero — Tue, 10 Mar 2020 09:42:57 GMT

Hi,

Just another comment, the RSSI accuracy of the radio in the PS is given in dB, not in dBm. dB is a ratio, so the same ratio of accuracy (percentage) will apply for both -30dBm and -90 dBm. I think this is usually called relative accuracy in the statistics instead of absolute accuracy.

Best regards,

Marjeris

RE: RSSI Accuracy in dBm

Marjeris Romero — Tue, 10 Mar 2020 09:13:01 GMT

Hi,

You are comparing two different things. The RSSI accuracy value that is listed on the Product Specification for nRF52840 refers to the RSSI accuracy internally on the radio.

The RSSI variation when radiated in the channel is a different thing, as many more variables are added, specially when measuring indoors, where you have reflections, multipath and interference.

If you want to measure the RSSI accuracy of the radio you need to perform the measurements conducted. This means using a cable soldered as closed as possible to the matching network on the nRF52840 and sending a constant carrier with a signal generator or protocol tester and reading the RSSI values then.

Best regards,

Marjeris