Re: [time-nuts] Flicker Noise Reduction
That's pretty slick. I think I see what's going on in there. It reminds me somewhat of optical chopping, but in this case, it looks like it's not about the 1/f LF/DC offsets adding to the amplitude, rather their effect on gain that's important. It seems to me that if the the gains are predictably correlated with the 1/f noise in the stages, then another approach may be to look at the actual 1/f noise (of the bias levels, not the THz signal) of the amplifier stages, and process it to provide continuous gain compensation, without a sampling system. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
Hi, On 2020-11-19 05:27, jimlux wrote: > On 11/18/20 7:15 PM, Richard (Rick) Karlquist wrote: >> >> On 11/18/2020 5:27 PM, jimlux wrote: >> >>> The proposed mitigation technique relies on tracking the >>> rapid gain variations in the radiometer due to 1/f noise and >>> correcting them by generating a baseline state in the first >>> amplification stage of the low noise amplifier (LNA). The >>> proposed 1/f noise mitigation method can be applied to any >>> receiver, but it is especially valuable for THz receivers since >> >> I'm confused here. My understanding of 1/f noise was >> that it was additive as in "AWGN". Can you clarify this? >> You also imply it works for ANY receiver. Now I'm REALLY >> confused. Unless the "direct conversion receiver" is actually >> an envelope detector. Then I think I see how it can work >> at any frequency. >> >> Not arguing, just trying to understand :-) >> >> Thanks. >> >> Rick N6RK > I was just copying from the intro to the paper. I'll read it tomorrow. > > My first glance is that they are talking about 1/f noise as gain > variations, and stabilizing that. Maybe for THz amps that's a thing. It seems that they aim to reduce the amplitude variations, and considering their detector that will for sure be visible, but it should also tell you about which frequencies they observe and thus which noise affects them. Not being able to use normal techniques to mitigate 1/f noise in amplifiers may be a major design hurdle at 670 GHz, who knows, that would probably take several articles to clarify. Personally, I find that 670 GHz is somewhat out of reach for my lab, so I can't say I have much experience up there. Oh, and for Johnsson noise and frequency, it's not white you know, it starts to slope more and more. The thermal noise obeys the Max Plank equation, but I have yet to see the proper derivations from that over to electrical noise, because you need to properly show the physics of a solid object and translation into electrical properties such as charge, volt and current. I'm sure someone done the work, I have just not found a really good reference for it, but it's fairly obvious from the hand-waving level. As you do radios in 67 GHz range I know that the slope is causing them issues, as it becomes noticable. There goes the low-frequency approximation. This is also relevant as the noise level and noise shape depends on temperature, which is used in radio astronomy on regular basis. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
On 11/18/20 7:15 PM, Richard (Rick) Karlquist wrote: On 11/18/2020 5:27 PM, jimlux wrote: The proposed mitigation technique relies on tracking the rapid gain variations in the radiometer due to 1/f noise and correcting them by generating a baseline state in the first amplification stage of the low noise amplifier (LNA). The proposed 1/f noise mitigation method can be applied to any receiver, but it is especially valuable for THz receivers since I'm confused here. My understanding of 1/f noise was that it was additive as in "AWGN". Can you clarify this? You also imply it works for ANY receiver. Now I'm REALLY confused. Unless the "direct conversion receiver" is actually an envelope detector. Then I think I see how it can work at any frequency. Not arguing, just trying to understand :-) Thanks. Rick N6RK I was just copying from the intro to the paper. I'll read it tomorrow. My first glance is that they are talking about 1/f noise as gain variations, and stabilizing that. Maybe for THz amps that's a thing. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
Attached is the block diagram of the receiver in essence an amplifier for which the effective input is gated/chopped on and off by turning the amplifier input FET on and off. Bruce > On 19 November 2020 at 16:15 "Richard (Rick) Karlquist" > wrote: > > > > On 11/18/2020 5:27 PM, jimlux wrote: > > > The proposed mitigation technique relies on tracking the > > rapid gain variations in the radiometer due to 1/f noise and > > correcting them by generating a baseline state in the first > > amplification stage of the low noise amplifier (LNA). The > > proposed 1/f noise mitigation method can be applied to any > > receiver, but it is especially valuable for THz receivers since > > I'm confused here. My understanding of 1/f noise was > that it was additive as in "AWGN". Can you clarify this? > You also imply it works for ANY receiver. Now I'm REALLY > confused. Unless the "direct conversion receiver" is actually > an envelope detector. Then I think I see how it can work > at any frequency. > > Not arguing, just trying to understand :-) > > Thanks. > > Rick N6RK > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
On 11/18/2020 5:27 PM, jimlux wrote: The proposed mitigation technique relies on tracking the rapid gain variations in the radiometer due to 1/f noise and correcting them by generating a baseline state in the first amplification stage of the low noise amplifier (LNA). The proposed 1/f noise mitigation method can be applied to any receiver, but it is especially valuable for THz receivers since I'm confused here. My understanding of 1/f noise was that it was additive as in "AWGN". Can you clarify this? You also imply it works for ANY receiver. Now I'm REALLY confused. Unless the "direct conversion receiver" is actually an envelope detector. Then I think I see how it can work at any frequency. Not arguing, just trying to understand :-) Thanks. Rick N6RK ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
On 11/18/20 4:59 PM, Richard (Rick) Karlquist wrote: I suspect that, whatever this is, only applies to 1/f mechanisms specific to THz, based on the last sentence. One of my former clients did a PhD at Stanford on 1/f noise and his dissertation certainly had no magic bullets to mitigate 1/f noise. There is some frequency, which I am fairly sure is less than a THz, above such that the usual equations for so-called Johnson noise no longer apply. FWIW. I don't blame you for not wanting to invest $15 or whatever it is only to see it and be disappointed. Are you sure the author(s) hasn't published a version of it on his own web page? I am guessing that this might be a reinvented transposed gain oscillator (TGO) used for the LO, where the LO is the original source of the noise. Rick N6RK On 11/18/2020 11:13 AM, Bruce Hunter via time-nuts wrote: Can anyone who subscribes to these transactions report on this? I dropped my subscription. In this letter, a novel 1/f noise mitigation technique is presented to improve the receiver 1/f noise performance of a 670 GHz receiver. Time domain 1/f noise corrected samples are compared with samples obtained without the correction. Spectral domain analysis shows that the 1/f noise mitigation method improves the receiver noise performance by 19 dB in the receiver under test. The presented 1/f noise mitigation technique can be applied to any direct-detection receiver in the THz frequency range.Published in: IEEE Transactions on Terahertz Science and Technology ( Early Access )Page(s): 1 - 1Date of Publication: 06 November 2020 The authors are at JPL, Northrup Grumman, and Colorado State, Ft Collins. Since it was funded by NASA, it will show up on JPL's tech report server in a bit. I'd send the author mehmet.o...@jpl.nasa.gov an email asking for a preprint copy. He should be happy to send it to you. Let me know if you need help - I've met some other co-authors (i.e. Al Tanner) but don't know them well. You might also check Colorado State's website - they might have a preprint up (or on arXive). It's targeting 670 GHz receivers for cubesats (TWICE is the project name) Not a Dicke Switch: The addition of a Dicke switch is useful for reducing 1/f noise in radiometers [5],[8]. However, only limited work on switches has been done at THz frequencies [9]. This, in turn, makes Dicke-switching architecture impractical for radiometry in the THz range. Therefore, a significant need exists to address 1/f noise in THz direct detection receivers The proposed mitigation technique relies on tracking the rapid gain variations in the radiometer due to 1/f noise and correcting them by generating a baseline state in the first amplification stage of the low noise amplifier (LNA). The proposed 1/f noise mitigation method can be applied to any receiver, but it is especially valuable for THz receivers since any switch inserted between the antenna and the low-noise amplifiers will add high insertion loss at these high frequencies, ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
I suspect that, whatever this is, only applies to 1/f mechanisms specific to THz, based on the last sentence. One of my former clients did a PhD at Stanford on 1/f noise and his dissertation certainly had no magic bullets to mitigate 1/f noise. There is some frequency, which I am fairly sure is less than a THz, above such that the usual equations for so-called Johnson noise no longer apply. FWIW. I don't blame you for not wanting to invest $15 or whatever it is only to see it and be disappointed. Are you sure the author(s) hasn't published a version of it on his own web page? I am guessing that this might be a reinvented transposed gain oscillator (TGO) used for the LO, where the LO is the original source of the noise. Rick N6RK On 11/18/2020 11:13 AM, Bruce Hunter via time-nuts wrote: Can anyone who subscribes to these transactions report on this? I dropped my subscription. In this letter, a novel 1/f noise mitigation technique is presented to improve the receiver 1/f noise performance of a 670 GHz receiver. Time domain 1/f noise corrected samples are compared with samples obtained without the correction. Spectral domain analysis shows that the 1/f noise mitigation method improves the receiver noise performance by 19 dB in the receiver under test. The presented 1/f noise mitigation technique can be applied to any direct-detection receiver in the THz frequency range.Published in: IEEE Transactions on Terahertz Science and Technology ( Early Access )Page(s): 1 - 1Date of Publication: 06 November 2020 Bruce Hunter ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
There is a paper from the univ of Twente in NL that seems to indicate that it takes some time in an open FET until the traps in the channel build up, so switching the FET off in a regular way might be an advantage. I stumbled across it when I was seeking input for my ultra-low-noise chopper amplifiers. Gerhard Am 19.11.20 um 00:38 schrieb Attila Kinali: On Wed, 18 Nov 2020 19:13:00 + (UTC) Bruce Hunter via time-nuts wrote: Can anyone who subscribes to these transactions report on this? I dropped my subscription. In this letter, a novel 1/f noise mitigation technique is presented to improve the receiver 1/f noise performance of a 670 GHz receiver. The paper in question is: "A Novel 1/f Noise Mitigation Technique Applied to a 670 GHz Receiver", by Ogut et al. https://doi.org/10.1109/TTHZ.2020.3036179 The description is extremely vague, but I think what they are doing is modulating the gain of the first LNA stage in an amplifier chain to get information on the total gain of the chain and correct for it. Which would make it basically a fancy chopper-amplifier that operates on the gain instead of the offset voltage. Attila Kinali "I have some vague idea that I could place behind the IEEE wall of shame. I won't work on it in the foreseeable future, but it may give me precedence if it turns out to be usable and I can count it as a publication, even if no one will read it." cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
Its just another variation on the principle of the Dicke radiometer. In their case the amplifier input device is turned off periodically by modulating its gate bias. https://www.engr.colostate.edu/ece/faculty/reising/pdf/journals/Ogut_et_al_T-TST_2020.pdf Bruce > On 19 November 2020 at 12:38 Attila Kinali wrote: > > > On Wed, 18 Nov 2020 19:13:00 + (UTC) > Bruce Hunter via time-nuts wrote: > > > Can anyone who subscribes to these transactions report on this? I dropped > > my subscription. > > In this letter, a novel 1/f noise mitigation technique is presented to > > improve the receiver 1/f noise performance of a 670 GHz receiver. > > The paper in question is: > "A Novel 1/f Noise Mitigation Technique Applied to a 670 GHz Receiver", > by Ogut et al. > https://doi.org/10.1109/TTHZ.2020.3036179 > > The description is extremely vague, but I think what they are doing > is modulating the gain of the first LNA stage in an amplifier chain > to get information on the total gain of the chain and correct for it. > Which would make it basically a fancy chopper-amplifier that operates > on the gain instead of the offset voltage. > > Attila Kinali > > -- > The driving force behind research is the question: "Why?" > There are things we don't understand and things we always > wonder about. And that's why we do research. > -- Kobayashi Makoto > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Flicker Noise Reduction
On Wed, 18 Nov 2020 19:13:00 + (UTC) Bruce Hunter via time-nuts wrote: > Can anyone who subscribes to these transactions report on this? I dropped my > subscription. > In this letter, a novel 1/f noise mitigation technique is presented to > improve the receiver 1/f noise performance of a 670 GHz receiver. The paper in question is: "A Novel 1/f Noise Mitigation Technique Applied to a 670 GHz Receiver", by Ogut et al. https://doi.org/10.1109/TTHZ.2020.3036179 The description is extremely vague, but I think what they are doing is modulating the gain of the first LNA stage in an amplifier chain to get information on the total gain of the chain and correct for it. Which would make it basically a fancy chopper-amplifier that operates on the gain instead of the offset voltage. Attila Kinali -- The driving force behind research is the question: "Why?" There are things we don't understand and things we always wonder about. And that's why we do research. -- Kobayashi Makoto ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
