CC1125: RSSI calculation with LNA gain

Rohal

Intellectual 495 points

Part Number: CC1125

Tool/software:

Dear Team,

I'm little bit confuse to calculate the RSSI

Signal strength at antenna is -110db and its amplified by LNA with a gain of 20db

Now what should be RSSI ?

-110 + 20 = 90 or -110

Does LNA improve the RF sensitivity ?

I'm using 19.2kbps air data rate, as per cc1125 data sheet receiving sensitivity should be -110 db(approx)

In my test set up if i'm giving -110 signal to the antenna port, cc1125 receive the signal but if signal desrease by 1 db (-111db) its not receiving any data.

Now the question is what's the receiving sensitivity of my board, -110db or -110 +20(LNA gain) =90db

over 1 year ago

0 Diego P over 1 year ago

TI__Expert 4860 points

Hi Vikas,

Sensitivity improvement will also depend on the noise figure of the LNA not just the gain. What is the noise figure of the LNA that you are using?

0 Rohal over 1 year ago in reply to Diego P

Intellectual 495 points

QPL9547 LNA has <.3db noise figure,

please let me know RSSI as per given data

0 Diego P over 1 year ago in reply to Rohal

TI__Expert 4860 points

Hi Vikas,

Theoretically you should see an improvement of about 5-6 dB in sensitivity based on an LNA with 19.5 dB of gain and 0.3 dB noise figure.

How are you feeding the signal to you antenna port? Is it an SMA cable or are you doing radiated testing?

Is the CC1125 and LNA on the same PCB?

0 Rohal over 1 year ago in reply to Diego P

Intellectual 495 points

Yes, it's a single board with CC1125 + LNA + RF switch + SMA connector

Signal feed by conducted way (RF CABLE), it not a radiated signal

and why 5-6 db improvement only theoretically it should be 19dB

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CC1125: RSSI calculation with LNA gain