GTT_2_Introduction nRF52 (Selectivity)

[Eugene]

In the GTT_2_Introduction nRF52 document there is a picture with text -42 dB Selectivity (2'nd CI). As far as i concerned it's about Carrier-to-interference ratio. But what exactly does it mean in that context?

[Håkon Alseth]

Hi Eugene,

The "carrier to interference" is a RX specific test. The DUT (Device-under-test) is receiving a modulated signal from the transmitter #1. At the same time, you inject a modulated signal from a transmitter #2, which has a lower signal amplitude.

This CI tests show how the RX of our DUT will handle two TX signals (where you want to receive one, and the other is considered noise). 2nd CI does the same thing, only with the noise-carrier shifted from the Fcenter, and the same principle is used for 3rd/4th etc.

You step up the signal strength of the noise to see where your receiver starts to lose packets (ie: received bit errors).

There's more about this here: en.wikipedia.org/.../Co-channel_interference

Cheers, Håkon