Hi Marcus, Thanks. Understood, that all makes sense to me. Part of this is I'm trying to understand the base Noise Figure as a starting point so I can design my filtered low noise front end as you suggest.
I guess you're confirming that 36.5dB is expected from the X440 and there's nothing crazy wrong about my math. Thanks, Steve On Wed, Aug 28, 2024, 3:15 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > 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). > > > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com >
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