RE: NRF52 RF Front End and link budget with/without external LNA

user116002 — Fri, 20 May 2022 11:31:36 GMT

RE: NRF52 RF Front End and link budget with/without external LNA

user116002 — Thu, 12 May 2022 08:35:56 GMT

Thank's for your response (and for pointing my mistake).
With my calculations, i'm trying to understand where the degradations of the SNR comes from
(why there is only 5dB of receiver sensivity improvment whith a 13dB LNA gain)

For the NRF52 Alone (if my understanding is correct) the is no mistake since the is only one stage (NRF52 AGC Gain)

-174dBm/Hz + 10log(1e6) + 15(SNRLoop) + 3(NRF52 estimated noise figure) = -96dBm input signal

I fix my mistake for the two cascaded devices : LNA (NF=2.7dB, G=13dB) and NRF52

I use the following formula (all values are linear)
NF(total) = LNA Noise + (NRF52 Noise – 1) / LNA Gain

-174dBm/Hz + 10log(1e6) + 15(SNRLoop) + (Total Noise Figure) - 13(LNA Gain) = -100dBm (witch is the max sensivity given in app note with external LNA)

The total Noise figure is estimated as 12dB. Since the noise figure of the LNA is 2.7dB and it's gain is 13dB
the noise figure of the NRF52 is estimated at 24.5 dB

Do you agree ?
Can i assume that, the degradation of the NRF52 noise figure is due to it's AGC ?? (lower gain, due to external LNA gain, and thus worst noise figure ?)

best regards

RE: NRF52 RF Front End and link budget with/without external LNA

user104202 — Wed, 11 May 2022 14:57:46 GMT

Hi,

What are you trying to achieve with these calculations?

The total noise figure for a network of cascaded two port devices is not the sum of the individual noise factors, so this calculation is not correct.

[quote user=""]confirm if the NRF52 front end use an AGC ?[/quote]

There is a AGC in the receiver front-end.

Best regards,

Bendik