The Receiver Noise figure should include sampling noise and ADC ENOB. Is that a free space path loss? You don't have any design margin for fades/blockages etc, so an External LNA might be a good idea. 3.6 dB NF isn't particularly low for a LNA, but it will help.
On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users <usrp-users@lists.ettus.com> wrote: > Hi, > > I am trying to calculate the link budget for USRP N310. > > Suppose I want a SNR of 20dB, > the signal bandwidth is 10MHz, > the thermal noise floor is -103.9dm. > Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz) > Rx Antenna Gain 6dBi > Path loss: 120dB > Tx Antenna Gain 6dBi > RF cable Loss (RX+TX): 1dB > > Then my TX power before TX antenna should be > -103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm > > The receive signal strength at RX port of USRP = -78.1dBm > The noise strength at RX port of USRP = -103.9dBm > The SNR before receiver is 25.8dB, after receiver is 20dB. > > However, due to the sampling noise and effective bits of ADC, I doubt that > the noise floor after the receiver would be much higher than -103.9dBm + > 5.8dB = -98.1dBm, e.g. -90dBm?, in that case my receive SNR would be lower > than 20dB. > > Does anyone know the output noise floor (or sensitivity) of USRP N310 > receiver (e.g. RX2 port) in 500-1000MHz band? e.g. in the unit of dBm/Hz? > > That would help me to decide if an external LNA is necessary. If so does > some typical wideband LNA with a gain of 20dB and noise figure of 3.6dB > would be enough. > > > Thank you! > > Regards, > Zhongyuan Zhao > > PhD Candidate, > Department of Computer Science & Engineering, > University of Nebraska-Lincoln > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
