Exact meaning of CN0 (carrier to noise)

[Armin Choopani]

Hi everyone

I am a little confused about CN0 and its relation with SNR. Does anyone know what is the exact meaning of CN0 and what is the difference between CN0 and SNR (signal to noise ratio)? I know higher CN0 translate into better accuracy.

In my design, I am using an active antenna. Does using an additional LNA (low noise amplifier), before the main IC, increase the CN0?

Any advice or help is appreciated.

Best Regards

Armin

[Karim RAMSI]

​Hi Armin,

the relation between CN0 (dB-Hz) and SNR (dB) is as below:

C/N0 (dB-Hz) = SNR + BW

For more detail, please see: https://insidegnss.com/measuring-gnss-signal-strength

If you are using an active Antenna, what you need is only a SAW filter. No need of additional LNA.

Hope it helps.

Best regards

Karim

[Armin Choopani]

Hi Karim

Thanks for your help, especially for the link you attached. Based on the formula you mentioned, adding an additional LNA degrades SNR and so CN0 too. But, in the Teseo III module that I have, an additional LNA is used before the main IC. Is that really necessary?

Kind Regards

Armin

[Karim RAMSI]

​Hi Armin,

TeseoIII chips embed an LNA but you need also external LNA to improve sensitivity by roughly 6dB to achieve -163dBm sensitivity. 

According to Friis Formula, the noise of the Receiver is determined by the first LNA performances. In our X-Nucleo-GNSS1A1, there is indeed an LNA on the board but if you are using in your design a active antenna, there is no need of additional LNA.

Regards

Karim

[Armin Choopani]

Hi Karim

Thank you. I wanted to get the best out of the IC. That is why I am tempted to use an additional LNA. But, as you said, there is no need for additional one.

Kind Regards

Armin