Ultra low frequency VCO
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From: Joel Koltner on 12 Jul 2010 14:30 Hi Jim, "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:s5mm365lej39010hb39ghkrsobfq4u9819(a)4ax.com... > I rarely keep track of OTC offerings, since I'm really in the > designing whole SOC business. Yeah, that's becoming a bit unfortunate for those of us doing board-level designs where the quantities just aren't there for doing custom ICs -- many of the RF parts that are left aren't particularly optimized for power consumption, since they're either parts that have been around forever (big transistors, I suppose) or they're aimed at the aerospace/military market where they figure you've got a nuclear reactor to power the thing. We're got a wireless handheld (battery-powered) widget that, between the numerous synthesized LOs, mixers, and amps might double as a pretty good hand-warmer. :-) ---Joel
From: Jim Thompson on 12 Jul 2010 14:42 On Mon, 12 Jul 2010 11:30:16 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: >Hi Jim, > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in >message news:s5mm365lej39010hb39ghkrsobfq4u9819(a)4ax.com... >> I rarely keep track of OTC offerings, since I'm really in the >> designing whole SOC business. > >Yeah, that's becoming a bit unfortunate for those of us doing board-level >designs where the quantities just aren't there for doing custom ICs -- many of >the RF parts that are left aren't particularly optimized for power >consumption, since they're either parts that have been around forever (big >transistors, I suppose) or they're aimed at the aerospace/military market >where they figure you've got a nuclear reactor to power the thing. > >We're got a wireless handheld (battery-powered) widget that, between the >numerous synthesized LOs, mixers, and amps might double as a pretty good >hand-warmer. :-) > >---Joel Post your questions and I'll try to answer. Larkin will certainly jump in and shovel a pile of BS in your direction :-) I'm thinking the way to resolve this Larkin statement, "... charge is not conserved" in... Message-ID: <3b893612tjjndo8o4v1evro050nonjgp41(a)4ax.com> is for me to post the solution on my website. BUT in a password-protected ZIP file. White-listed individuals can contact me for the password and see how it works, that way Larkin will be prevented from seeing it and claiming "that's what I really meant... let him choke on his own drool :-) I'll let you know when it's up there. Funny. Yesterday, while cooling my heels at a going-away swim party for a granddaughter (they're moving to Rancho Mirage... Renee's father is in ill-health, so she's going to run his automotive parts business), I sat there in the shade, in 112�F heat and "played" the circuit in my head... that's how I figured out where the missing charge comes from ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Obama isn't going to raise your taxes...it's Bush' fault: Not re- newing the Bush tax cuts will increase the bottom tier rate by 50%
From: JosephKK on 12 Jul 2010 22:57 On Mon, 12 Jul 2010 09:37:07 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >JosephKK wrote: >> On Fri, 9 Jul 2010 10:22:34 -0700 (PDT), j <jdc1789(a)gmail.com> wrote: >> >>> Resolution of noise vs frequency, (as in bw), is the issue in phase >>> noise measurements. The OP never stated the offset from the carrier >>> nor bandwidth. Or maybe I just missed it. >>> >>> Itâs not clear to me why JosephKK thinks this would be either a time >>> consuming or difficult measurement to make. Assuming the appropriate >>> measurement system is in hand 100 dBc numbers are easily achievable. >>> Whether itâs 60 Hz or several GHzâs the global issues are the same in >>> making a phase noise measurement. >>> >>> But having said the above, without the OP responding I guess it really >>> doesnât matter. But Iâd like to know more about the application and >>> derive solutions from there. >> >> >> OK. For a carrier of 60 MHz. Pick an instrument or test setup of your >> choice, state the model[s]. Clearly explain just what is going on in the >> measurement and the time it takes to accumulate sufficient data to make >> the measurement. Explain why it takes that much time to reach a reliable >> measurement of -100 dBc phase noise at that carrier frequency. >> >> Now see how well it scales to one million times lower fundamental >> frequency without a similar scaling in measurement time. > >It's the modulation frequency that's relevant, not the carrier >frequency. Measurements get slower when you reduce the bandwidth. > >(You can see why this doesn't work if you imagine running it >backwards--mixing or multiplying up to some very high frequency doesn't >allow you to make a measurement with 1 Hz bandwidth any faster. > > >Cheers > >Phil Hobbs Now what is the equivalent bandwidth of -100 dBc for a 60 Hz carrier? Since you said 20 log() basis 60 * 10^-5 is 600 microHz. That would have to take some minutes, and if you wanted a proper 10 to 1 measurement buffer, it takes ten times longer. Call it 10,000 seconds? A few hours. And the reference stability etc., i remarked on is coming into play.
From: JosephKK on 12 Jul 2010 23:02 On Mon, 12 Jul 2010 09:39:54 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >JosephKK wrote: >> On Fri, 09 Jul 2010 11:56:28 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> On 7/9/2010 8:59 AM, JosephKK wrote: >>>> On Thu, 08 Jul 2010 15:37:28 -0400, Phil Hobbs >>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>> >>>>> Phil Hobbs wrote: >>>>> >>>>>> I don't know that -100 dBc/Hz is that hard at 60 Hz. I bet you could do >>>>>> that by running a bog standard multivibrator at 1024*1024*60 Hz and >>>>>> dividing down. You'd need a sine shaper, but the phase noise goes down >>>>>> by N**2, so you'd get 100 dB improvement just from that. Alternatively, >>>>>> you could make an LC VCO and divide that down. >>>>> 120 dB. Can't count today. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> Sure, you can mathematically "predict" it, but how do you measure it? >>>> Or do you switch to another metric which can be both predicted and >>>> measured? >>> Let's keep the math bashing to the other thread, okay? >>> >>> Although it isn't highly relevant to the OP's problem, it wouldn't be >>> very difficult to measure the residual FM--use MOSFET buffers to drive >>> two divider strings running from independent power supplies, and >>> cross-correlate their outputs, exchanging them periodically to get rid >>> of the drift in the correlator. For the correlator design, see Hanbury >>> Brown and Twiss, circa 1963--and they did it with discrete bipolars. >>> >>> There are hard measurements, but this isn't one of them. >>> >>> Cheers >>> >>> Phil Hobbs >> >> My issue was not so much the direct difficulty of the measurement, there >> are several fairly straight forward setups. But with the _time_ it would >> take to make the measurement using many of those setups. The elapsed >> time seriously aggravates other measurement issues, notably including >> calibration. > >Modulation frequency isn't affected by heterodyning or frequency >multiplication and division. If you take a 60 MHz sine wave and FM it >at 1 Hz modulation frequency and 1 MHz peak frequency deviation (M=1E6), > then divide it by a million, you get a 60-Hz sine wave modulated at 1 >Hz with a 1-Hz peak frequency division (M=1). > >Cheers > >Phil Hobbs I am sorry. I think i am misreading your post, are you saying you can get a 1 MHz deviation on a 60 Hz carrier? Naw, you must be trying to say something else and i misunderstood.
From: Phil Hobbs on 12 Jul 2010 23:23
JosephKK wrote: > On Mon, 12 Jul 2010 09:37:07 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> JosephKK wrote: >>> On Fri, 9 Jul 2010 10:22:34 -0700 (PDT), j <jdc1789(a)gmail.com> wrote: >>> >>>> Resolution of noise vs frequency, (as in bw), is the issue in phase >>>> noise measurements. The OP never stated the offset from the carrier >>>> nor bandwidth. Or maybe I just missed it. >>>> >>>> It's not clear to me why JosephKK thinks this would be either a time >>>> consuming or difficult measurement to make. Assuming the appropriate >>>> measurement system is in hand 100 dBc numbers are easily achievable. >>>> Whether it's 60 Hz or several GHz's the global issues are the same in >>>> making a phase noise measurement. >>>> >>>> But having said the above, without the OP responding I guess it really >>>> doesn't matter. But I'd like to know more about the application and >>>> derive solutions from there. >>> >>> OK. For a carrier of 60 MHz. Pick an instrument or test setup of your >>> choice, state the model[s]. Clearly explain just what is going on in the >>> measurement and the time it takes to accumulate sufficient data to make >>> the measurement. Explain why it takes that much time to reach a reliable >>> measurement of -100 dBc phase noise at that carrier frequency. >>> >>> Now see how well it scales to one million times lower fundamental >>> frequency without a similar scaling in measurement time. >> It's the modulation frequency that's relevant, not the carrier >> frequency. Measurements get slower when you reduce the bandwidth. >> >> (You can see why this doesn't work if you imagine running it >> backwards--mixing or multiplying up to some very high frequency doesn't >> allow you to make a measurement with 1 Hz bandwidth any faster. >> >> >> Cheers >> >> Phil Hobbs > > Now what is the equivalent bandwidth of -100 dBc for a 60 Hz carrier? > Since you said 20 log() basis 60 * 10^-5 is 600 microHz. That would have > to take some minutes, and if you wanted a proper 10 to 1 measurement > buffer, it takes ten times longer. Call it 10,000 seconds? A few hours. > And the reference stability etc., i remarked on is coming into play. You're confused, I'm afraid. -100 dBc phase noise in a given bandwidth (say 1 Hz, but it doesn't matter) is 7 microradians RMS. Using a 5V swing and a CMOS analogue gate as a phase detector, that's dV = 7e-6 rad RMS * 5V/(pi rad) = 11 microvolts RMS, which is trivial to measure in a 1 Hz bandwidth in a few seconds--it's 80 dB above the noise of a good op amp, so you just have to wait for the filter to settle. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |