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] Survey grade antennas
Hi If you dig into the data on the antennas …. ( they are fully tested and doccumented …) The Novatel design does a *very* good job. Indeed they are *much* better than an old style giant choke ring design. Normal list price is roughly 10X what that listing shoed. Similar antennas normally sell for $600 to $1200 on eBay. Indeed the 703 GGG *is* discontinued as a brand new product. That’s also true of a number of pretty expensive antennas you see on eBay. These are *not* the same thing as the low cost stuff from China. Bob > On Nov 18, 2020, at 5:49 PM, Charles Steinmetz wrote: > > Stu wrote: > > >> The usual auction site has a few true survey grade antennas for a very good > >> price. Search for Novatel GPS-703-GGG. These cover all three frequency > >> bands (L1, L2, L5), which is still unusual to find in surplus. > > Bob wrote: > >> ….. and now they all seem to have been sold > > If you look at the auctions linked from that one, you will find dozens of > other listings for similar multi-band antennas -- some of them considerably > less expensive than the Novatel. > > Note that the Novatel information admits that the antenna is not a choke ring > design, but instead claims that it provides "Choke ring antenna functionality > without the size and weight." Also note that the Novatel datasheet makes no > reference to it being a survey-grade antenna. > > I did not look carefully at the listings for the other tri-band "survey" > antennas on ebay, but I assume the same is true of them. > > Best regards, > > Charles > > > > ___ > 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
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] Survey grade antennas
On 11/18/20 2:49 PM, Charles Steinmetz wrote: Stu wrote: >> The usual auction site has a few true survey grade antennas for a very good >> price. Search for Novatel GPS-703-GGG. These cover all three frequency >> bands (L1, L2, L5), which is still unusual to find in surplus. Bob wrote: ….. and now they all seem to have been sold If you look at the auctions linked from that one, you will find dozens of other listings for similar multi-band antennas -- some of them considerably less expensive than the Novatel. Note that the Novatel information admits that the antenna is not a choke ring design, but instead claims that it provides "Choke ring antenna functionality without the size and weight." Also note that the Novatel datasheet makes no reference to it being a survey-grade antenna. There are a lot of clever designs out there intended for "top of pole in a survey" kind of use that are quite good at suppressing multipath. A lot of interesting dielectric lenses and arrangement of multiple radiators within the radome. Like that weird multispiral design, or the 3D choke of spikes instead of the more traditional nested cake pans. Survey in the "let's go out and stake the construction site" (so uncertainties of few mm + 1ppm of baseline length for differential) but not in the geodetic "let's measure the plate movement in my backyard with a post driven 50 feet into the bedrock" sense. ___ 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.
Re: [time-nuts] Survey grade antennas
Stu wrote: >> The usual auction site has a few true survey grade antennas for a very good >> price. Search for Novatel GPS-703-GGG. These cover all three frequency >> bands (L1, L2, L5), which is still unusual to find in surplus. Bob wrote: ….. and now they all seem to have been sold If you look at the auctions linked from that one, you will find dozens of other listings for similar multi-band antennas -- some of them considerably less expensive than the Novatel. Note that the Novatel information admits that the antenna is not a choke ring design, but instead claims that it provides "Choke ring antenna functionality without the size and weight." Also note that the Novatel datasheet makes no reference to it being a survey-grade antenna. I did not look carefully at the listings for the other tri-band "survey" antennas on ebay, but I assume the same is true of them. Best regards, Charles ___ 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] Flicker Noise Reduction
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.
Re: [time-nuts] Surplus Navicom GPSDO
I see that Mark Sims examined this Navicom GPSDO in March 2019 (EEVblog). https://www.eevblog.com/forum/metrology/navicom-rcgd-m-gpsdo/ gb == Date: Sat, 14 Nov 2020 15:52:08 -0600 From: Greg Beat To: time-nuts@lists.febo.com Subject: [time-nuts] Surplus Navicom GPSDO Surplus Navicom RCGD-M units have recently appeared on eBay, https://www.ebay.com/itm/312306372323 from reseller ?EYT_GPS? (Shenzhen, China). Lady Heather (used by reseller) identifies Navicom GPS receiver as Motorola (looks like Oncore footprint). A bit of a mystery to the reseller, outputs/inputs to the FGPA on boards. Tight, stacked assembly. == He has another unit, (cheaper) that uses the Furuno GT-8031F GPS receiver module and an unknown OCXO. https://www.ebay.com/itm/312306276819 == Have fun experimenting! greg, w9gb ___ 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] Survey grade antennas
Hi ….. and now they all seem to have been sold :) Thanks for the heads up !!! Bob > On Nov 18, 2020, at 3:56 AM, Stewart Cobb wrote: > > The usual auction site has a few true survey grade antennas for a very good > price. Search for Novatel GPS-703-GGG. These cover all three frequency > bands (L1, L2, L5), which is still unusual to find in surplus. > > (No connection to seller, just passing along a good deal.) > > Cheers! > --Stu > ___ > 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.
[time-nuts] Survey grade antennas
The usual auction site has a few true survey grade antennas for a very good price. Search for Novatel GPS-703-GGG. These cover all three frequency bands (L1, L2, L5), which is still unusual to find in surplus. (No connection to seller, just passing along a good deal.) Cheers! --Stu ___ 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.
