RX/TX separation for x40

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OskarM
Posts: 19
Joined: Sun Dec 09, 2018 3:02 pm

RX/TX separation for x40

Post by OskarM » Mon Jan 21, 2019 1:28 pm

Hi,
is there any specification with regards to RX <-> TX separation for the x40 board?

I have a setup where LNA is into RX and the TX goes into GNSS recevier - a commercial grade GNSS receiver that claims to have -160dBm sensitivity. With active antenna and additional LNA I can have up to 50dB of gain for GPS band - that would mean signals up to -80dBm at RX port (best case open sky signal strength for GPS is -130dBm). I don't see that the gnss module is able to sync when rx/tx are off, but the reported signal strength is non-zero - thus the question.

I have seen LMS FAQ p5.16 with TX -> RX separtion in terms of noise density @ TX dBms :
Band 1 -135dBm/Hz with TX output -2.2 dBm/3.84
So : -135dbm/hz @3.84Mhz -> 10^(-135/10) * 3.84e6 ->10*log10()-> -69dbm (band 1 is 2100Mhz)

- from calcualtions it seems to be roughly 70db - is that correct? Would that mean that -80dbm on RX port could have -150dBm on TX? Getting more gain at RX would mean the risk of coupling the signal from RX to TX directly then?

thanks, best regards

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