Timeline for Direct-digital phase noise measurement reference phase scaling
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 22, 2023 at 17:15 | comment | added | MattHusz | Wouldn't scaling prevent you from cancelling the clock jitter ($\phi_{\mathrm{clk}}$) in the subtraction? | |
| Aug 22, 2023 at 1:08 | comment | added | Marcus Müller | I don't think that is possible! | |
| Aug 22, 2023 at 0:32 | comment | added | MattHusz | Ok I think I now understand that part. Thanks for taking the time to explain and re-explain. So would you then, later (eg after subtraction), compensate to nullify the change in the phase noise variance caused by scaling? | |
| Aug 21, 2023 at 23:41 | comment | added | Marcus Müller | They're directly determining the phase velocity of the mixture product. So unless you want a phase that spins with the difference in frequency, you need to make the reference phase spin as fast as the phase of dut. So, you achieve exactly that by multiplication of the slower-by-a-factor-of-$m$ phase with $m$. | |
| Aug 21, 2023 at 23:32 | comment | added | MattHusz | Hm, I still don't follow. If, using their example of a 10 MHz DUT and 5 MHz ref, we downconverted both channels using a 10 MHz I/Q DDS and LPF'd and decimated, the band around the reference carrier would be completely filtered out. Scaling isn't performed until after phase detection. Bear with me here, I expect I'm just still not understanding what you (and the paper) are saying... | |
| Aug 21, 2023 at 23:23 | comment | added | Marcus Müller | Well the sentence from the paper that I quote directly contradicts that, and the phase factor does, too. | |
| Aug 21, 2023 at 23:20 | comment | added | MattHusz | The NCOs can be set independently for the DUT and reference channels. So, the phase of each channel, not ignoring frequency drift, is $\phi_1 (t) = (\omega_{\mathrm{nco(dut)}} - \omega_{\mathrm{dut}}) t + \phi_{\mathrm{dut}} + \phi_{\mathrm{adc1}} + \phi_{\mathrm{clk}}$ and $\phi_2 (t) = (\omega_{\mathrm{nco(ref)}} - \omega_{\mathrm{ref}}) t + \phi_{\mathrm{ref}} + \phi_{\mathrm{adc2}} + \phi_{\mathrm{clk}}$. Sorry, I probably could have been clearer on this point. Anyway, I do think $\omega_{\mathrm{nco(dut)}}=\omega_{\mathrm{dut}}$, etc. Or at least approximately so. Or did I misunderstand? | |
| Aug 21, 2023 at 22:18 | history | answered | Marcus Müller | CC BY-SA 4.0 |