For an ADC, I believe the noise power is fairly constant. As sample rate increases, noise power density should decrease and SNR should improve. Thus a measured improvement in noise figure.
Source: https://www.analog.com/en/resources/technical-articles/noise-spectral-density.html x310 ADC (ADS62P48): http://www.ti.com/lit/ds/slas635b/slas635b.pdf Mark On Mon, Mar 3, 2025, 7:48 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 03/03/2025 22:23, Dustin Widmann via USRP-users wrote: > > Hi all, > > > > I see an interesting trend and I'm not sure how to explain it ... > > > > I've done a y-factor measurement, sweeping the frequency, sampling > > rate, and rx-gain with an x310 with the SBX-120 daughterboard. The > > results seem similar to the published performance specs. The part I'm > > not sure quite how to explain is why the NF would vary with the > > sampling rate. Doesn't the X310 use a static sample rate and > > downsample in the FPGA? Why would this affect the NF? Why does the > > effect seem to be more exaggerated at higher gain settings? Why is the > > effect on NF very small at higher sampling rates but more pronounced > > at lower ones instead of being a linear change? > > > > Dustin > > > What noise inputs are you using for the two levels in your Y-factor? > > The amount of power represented at each sample-rate is different, and > shooting from the hip here, the amount of energy > represented in the transition regions at different sample rates will > be different. For example, odd/even/factor-of-4 > sample-rates have different pass-band shapes. > > > _______________________________________________ > 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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