On 28/08/2024 18:04, Steve Hamn wrote:
Hello,
I have been trying to estimate the Noise Figure of the X440. I looked
through all the documentation I could find and couldn't find it
anywhere, so I tried to calculate it myself.
It looks like the ZU2xDR RFSoC has a NSD of -146dBFS/Hz @ 2.4GHz
(https://docs.amd.com/r/en-US/ds926-zynq-ultrascale-plus-rfsoc/RF-ADC-Performance-Characteristics)
and the Full Scale Input is 1Vppd (0.707Vrms) @ 100ohms
(https://docs.amd.com/r/en-US/ds926-zynq-ultrascale-plus-rfsoc/RF-ADC-Electrical-Characteristics)
.
Based on this information I calculate NSD of -139dBm/Hz [-146dBFS/Hz +
10log10(0.707^2/100Ω*1000)], so -139dBm/Hz - -174dBm/Hz gives Noise
Figure of 35dB? Add the 1.5 insertion loss of the TCM2-63WX+ on the
Daughterboard (https://files.ettus.com/manual/page_fbx.html), gives an
approximate noise figure of the X440 at 36.5dB for 2.4GHz.
Is this correct? Seems high, I don't have much experience calculating
noise figure from ADC's so I'm wondering if I'm missing something.
Thanks,
Steve
"Naked" ADCs are inherently very very noisy devices. Since the X440 has
no RF pre-processing of any importance, you'd at
least need a low-noise filtered front-end to beat the inherent ADC
noise into insignificance. For other USRP radios, mostly,
that's already taken care of, and the receiver noise-figure is much
more "respectable" (not, radio astronomy respectable,
but adequate to put onto an over-the-air antenna).
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