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?

[Øyvind Karlsen]

LO is the local oscillator, this is used in mixers in order to get a signal to the desired frequency. Higher frequencies generally have higher attenuation and will be easier to suppress because of this.

The properties of the reciever changes when the bitrate changes, this is partly due to lowered sensitivity for higher bitrates.

[Eugene]

I meant what the LO frequency was (i understand that it changes because of hopping). What's the IF (intermediate frequency) in this case?

[Øyvind Karlsen]

For 2Msps mode the LO is 2MHz below the carrier, the IF is 2MHz. For 1Msps mode the LO is 1MHz below carrier, the IF is 1MHz.