Channel interference

[ock]

I have a NRF52840 and wanted to know, how much of a signal gets into another channel in BLE. I am going to explain what I mean so there is no confusion :).

The Bluetooth Channels are like following image shows: BLE channel

So there are 40 channel with a bandwitdth of 2MHz, and the center frequencies are 2 MHz apart.

Now let's suppose I am sending on channel 20.

How much of this signal would land in channel 19 / 21? I got the following from the BLE specifications: Specs

I am not sure which row gives me the information I need. I hope you can help me.

[Jørn]

Hello ock

The lists you link to are the requirements for the receiver. They list the requirement for Carrier/Interference ratio, while maintaining a maximum bit error rate (BER) of 0.1%. If you look at the nRF52840 table 22.15.6 RX selectivity, our numbers are lower than the ones listed in the Bluetooth specification. This indicates our chip can handle worse C/I ratios than the requirement while maintaining a maximum BER of 0.1%.

If you look at table 22.15.4 of the nRF52840 product specification you find the Transmitter specification. Here it is stated that the ratio between transmit power 1 MHz from the carrier is -23dB when compared to the output power of the carrier. Similarly for 2MHz from the carrier frequency it is listed as -50dB compared to the carrier output power. These numbers are for the 1Mb/s PHY.

Considering each channel center frequency are 2 MHz apart, you could expect to see, in channel 19 and 21, a signal whose power is around -50dB compared to the output power in channel 20.

Best regards

Jørn Frøysa