On Sep 29, 2:25=A0pm, me0...@yahoo.com wrote:> On Sep 29, 9:11=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Sep 28, 5:38=A0pm, Bill Sloman <bill.slo...@ieee.org> wrote: > > > > On Sep 28, 9:41=A0pm, George Herold <gher...@teachspin.com> wrote: > > > > > On Sep 28, 1:41=A0pm, "Michael A. Terrell" <mike.terr...@earthlink.=net>> > > > wrote: > > > > > > George Herold wrote: > > > > > > > Yeah DDS from a micro looks like the 'best' path. =A0It's just =outside> > > > > > my present comfort zone and so hard to predict how long it will > > > > > > take. > > > > > > =A0 =A0You can get a "AD9850 Module DDS Signal Generator with Cir=cuit> > > > > Diagram" in ebay for about $13 and demo software on the Analog De=vices> > > > > website. =A0There is also VB source code & 80*51 source code avai=lible for> > > > > free. > > > > > > =A0 =A0I just bought a couple for a project I'm working on. > > > > > > -- > > > > > You can't have a sense of humor, if you have no sense. > > > > > Thanks Michael, =A0there's so many DDS chips. =A0Which ones will st=ill be> > > > around in ten years? > > > > The first mention of the AD9850 I can find here dates back to 2000, s=o> > > it has been around for more than ten years already - always a good > > > sign - and I think that it had been around for a while then. IIRR it > > > was the first of Analog Devices DDS chips, and it seems to have been > > > designed into a lot of applications, so it may be around for a while > > > yet. > > > > -- > > > Bill Sloman, Nijmegen- Hide quoted text - > > > > - Show quoted text - > > > Thanks Bill, that's good to know. > > > George H.- Hide quoted text - > > > - Show quoted text - > > George, > > What kind of tuning resolution do you need?- Hide quoted text - > > - Show quoted text -Hi MeO, The product will be doing all sorts of Fourier analysis. At the moment I think the reason for the VCO is only to look at sidebands*. And mostly sidebnads at a high modulation index... So I'd like to modulate it with a (say) 1kHz sine wave and see sidebands out to maybe the 7th to 10th harmonic. I'm not sure how to turn this into a resolution spec. George H. *It would be nice if we had some other 'physics' to do with the VCO. Then I might have some 'real' specs.
50 kHz VCO w/sine output
Started by ●September 27, 2011
Reply by ●September 30, 20112011-09-30
Reply by ●September 30, 20112011-09-30
On Sep 29, 4:05=A0pm, Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net> wrote:> On 09/29/2011 12:11 PM, George Herold wrote: > > > > > > > On Sep 28, 4:33 pm, me0...@yahoo.com wrote: > >> On Sep 28, 12:34 pm, George Herold<gher...@teachspin.com> =A0wrote: > > >>> On Sep 28, 1:38 pm, Tim Wescott<t...@seemywebsite.com> =A0wrote: > > > <big snip> > >>> - Show quoted text - > > >> Hey George, > > >> Here s some more food for thought re the downconverter approach: > > > Hi MeO > > >> (you ve never said what you re looking for in Frequency stability, but > >> I m assuming you want accuracy set by your XOSC and phase noise is > >> really not an issue) > > > Hmm, this is a small part of a new project. =A0I'm still trying to get =a> > handle on the specs I need. > > >> If you ve never done this before I would discourage you: > > >> 1) =A0 =A0 =A0 Unless you ve got the time to put into the learning cur=ve, not> >> only RF but the Freq Synth part > >> 2) =A0 =A0 =A0You have access to a decent SA or FFT analyzer that can =cover your> >> frequency of interest > >> 3) =A0 =A0 =A0A low frequency network analyzer would also make the job=a lot> >> easier > > > Well, an RF amplifier design ~20 years ago. =A0(would have been nice to > > have a spectrum analyzer at the time, I had some ring down issues in > > one of the amp stages.) =A0The only RF recently is a few watt oscillato=r> > for a Rubidium discharge lamp. =A0(Where frequency stability is not muc=h> > of an issue.) =A0I've got a 'new' SRS770 spectrum analyzer, (DC-100kHz) > > which should tell me all I need to know about what's happening after > > the mixer. > > >> You ve got another potential problem when you attempt this kind of > >> frequency translation. =A0The low Q VCO is going to have a tendency to > >> be pulled around by the high Q XOSC. =A0They sniff each other when > >> they get close frequency wise. > > > Hmm a bit of padding should take care of that... I'll just burn > > power! > > >> So you have to make sure your system has enough isolation between the > >> two oscillators. =A0You need to take into account things like LO to RF > >> isolation when looking at the mixer. =A0In S parameter terms it will > >> be the S12 term of the VCO chain. > > >> Again I will state, I really believe your VCO will have to be phased > >> locked. =A0Otherwise it ll be hit and miss when trying to set it s > >> freq. =A0Each one of those gain curves will be slightly different from > >> part to part. > > >> I don t mean to discourage you. =A0In fact, for somebody that does syn=th> >> design this is pretty trivial. > > >> But for a first timer it will be daunting, and could really end up > >> being a big waste of time. =A0The digital approach is just a matter of > >> ramping up and not equipment intensive. =A0And software is comparative=ly> >> easier to change then hardware. > > > Thanks, =A0I'd like to do a DDS design sometime, but right now that > > looks like a longer learning curve/ time sink. =A0(strange as that may > > sound.) > > >> I m just trying to be helpful and I wish you the best of luck. > > > Thanks again. =A0At the moment I'm just going to order some VCO's from > > minicirciuts... (throw some money at the problem.) and see what the > > output looks like. =A0I'll also push forward on the triangle wave/ sine > > shaper idea. > > > This is a nice app note, > >http://www.national.com/an/AN/AN-263.pdf > > > George H. > > >> Btw, you do want to go with frequencies up over 10MHz. =A0Get far away > >> from your baseband, just makes the IF filtering all that much > >> easier.- Hide quoted text - > > >> - Show quoted text - > > As I posted to the sample-hold thread by mistake: > > Using a CD4017 and some resistors will get rid of all harmonics up to > the ninth, so a fixed LPF will make a nice sine wave with 3:1 tunability. > > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs > Principal Consultant > ElectroOptical Innovations LLC > Optics, Electro-optics, Photonics, Analog Electronics > > 160 North State Road #203 > Briarcliff Manor NY 10510 > 845-480-2058 > > hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted tex=t -> > - Show quoted text -Hi Phil, CD4017? A decade counter. Summing different 'fractions' into an opamp to get a 'stepped' sine wave? Color me confused. George H.
Reply by ●September 30, 20112011-09-30
On Sep 29, 7:25=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My- Web-Site.com> wrote:> On Thu, 29 Sep 2011 12:40:32 -0500, Frnak McKenney > > > > > > <fr...@far.from.the.madding.crowd.com> wrote: > >On Tue, 27 Sep 2011 12:44:44 -0700 (PDT), George Herold <gher...@teachsp=in.com> wrote:> >> On Sep 27, 2:17 pm, Tim Wescott <t...@seemywebsite.com> wrote: > >>> On Tue, 27 Sep 2011 09:54:36 -0700, George Herold wrote: > > >>> > 30kHz to 100kHz VCO with sine wave output. > > > =A0 [...] > > >> Hi Tim, =A0I've got a spice simulation with just diode limiting for th=e> >> varible gain. =A0~1.2 Vp-p on the output. =A0I couldn't find any varac=tors> >> in LTspice so I just used a diode and added some more C in parallel. > > >George, > > >You may have already achieved a useful solution, but I did run > >across a numnber of potential models using the following search > >string: > > > =A0+spice|ltspice +model varactor|vvc > > >including these: > > > =A0Varactor SPICE Models for RF VCO Applications - Skyworks > > =A0http://www.skyworksinc.com/uploads/documents/200315B.pdf > > > =A0Spice Models for Aeroflex / Metelics GaAs Hyperabrupt Varactor > > =A0http://www.aeroflex.com/ams/Metelics/pdfiles/MGV_spice_models.pdf > > >and Infineon has some spice models for (e.g.) its BB535 varactor. > >Got to: > > > =A0http://http://www.infineon.com/ > > >and search for BB535. > > >Hope one of these helps. > > >Frank McKenney > >-- > > =A0"Expecting the world to treat you fairly because you are good is > > =A0 like expecting the bull not to charge because you are a > > =A0 vegetarian." =A0 =A0 =A0 =A0 =A0 =A0 =A0-- Dennis Wholey > > Do it with the exact data... > > www.analog-innovations.com/VVC.zip > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ==A0 =A0...Jim Thompson> -- > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 [On the Road, in New York] > > | James E.Thompson, CTO =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ==A0 =A0| =A0 =A0mens =A0 =A0 |> | Analog Innovations, Inc. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ==A0 | =A0 =A0 et =A0 =A0 =A0|> | Analog/Mixed-Signal ASIC's and Discrete Systems =A0| =A0 =A0manus =A0 ==A0|> | Phoenix, Arizona =A085048 =A0 =A0Skype: Contacts Only =A0| =A0 =A0 =A0 ==A0 =A0 =A0 |> | Voice:(480)460-2350 =A0Fax: Available upon request | =A0Brass Rat =A0| > | E-mail Icon athttp://www.analog-innovations.com| =A0 =A01962 =A0 =A0 | > > I love to cook with wine. =A0 =A0 Sometimes I even put it in the food.- H=ide quoted text -> > - Show quoted text -Thanks Jim, I saved it. I've got so many ways to 'skin this cat' now. I don't think that I'll be using a varactor. (at least for the first try.) George H.
Reply by ●September 30, 20112011-09-30
On Sep 30, 11:01=A0am, George Herold <gher...@teachspin.com> wrote:> On Sep 29, 4:05=A0pm, Phil Hobbs > > > > <pcdhSpamMeSensel...@electrooptical.net> wrote: > > On 09/29/2011 12:11 PM, George Herold wrote: > > > > On Sep 28, 4:33 pm, me0...@yahoo.com wrote: > > >> On Sep 28, 12:34 pm, George Herold<gher...@teachspin.com> =A0wrote: > > > >>> On Sep 28, 1:38 pm, Tim Wescott<t...@seemywebsite.com> =A0wrote: > > > > <big snip> > > >>> - Show quoted text - > > > >> Hey George, > > > >> Here s some more food for thought re the downconverter approach: > > > > Hi MeO > > > >> (you ve never said what you re looking for in Frequency stability, b=ut> > >> I m assuming you want accuracy set by your XOSC and phase noise is > > >> really not an issue) > > > > Hmm, this is a small part of a new project. =A0I'm still trying to ge=t a> > > handle on the specs I need. > > > >> If you ve never done this before I would discourage you: > > > >> 1) =A0 =A0 =A0 Unless you ve got the time to put into the learning c=urve, not> > >> only RF but the Freq Synth part > > >> 2) =A0 =A0 =A0You have access to a decent SA or FFT analyzer that ca=n cover your> > >> frequency of interest > > >> 3) =A0 =A0 =A0A low frequency network analyzer would also make the j=ob a lot> > >> easier > > > > Well, an RF amplifier design ~20 years ago. =A0(would have been nice =to> > > have a spectrum analyzer at the time, I had some ring down issues in > > > one of the amp stages.) =A0The only RF recently is a few watt oscilla=tor> > > for a Rubidium discharge lamp. =A0(Where frequency stability is not m=uch> > > of an issue.) =A0I've got a 'new' SRS770 spectrum analyzer, (DC-100kH=z)> > > which should tell me all I need to know about what's happening after > > > the mixer. > > > >> You ve got another potential problem when you attempt this kind of > > >> frequency translation. =A0The low Q VCO is going to have a tendency =to> > >> be pulled around by the high Q XOSC. =A0They sniff each other when > > >> they get close frequency wise. > > > > Hmm a bit of padding should take care of that... I'll just burn > > > power! > > > >> So you have to make sure your system has enough isolation between th=e> > >> two oscillators. =A0You need to take into account things like LO to =RF> > >> isolation when looking at the mixer. =A0In S parameter terms it will > > >> be the S12 term of the VCO chain. > > > >> Again I will state, I really believe your VCO will have to be phased > > >> locked. =A0Otherwise it ll be hit and miss when trying to set it s > > >> freq. =A0Each one of those gain curves will be slightly different fr=om> > >> part to part. > > > >> I don t mean to discourage you. =A0In fact, for somebody that does s=ynth> > >> design this is pretty trivial. > > > >> But for a first timer it will be daunting, and could really end up > > >> being a big waste of time. =A0The digital approach is just a matter =of> > >> ramping up and not equipment intensive. =A0And software is comparati=vely> > >> easier to change then hardware. > > > > Thanks, =A0I'd like to do a DDS design sometime, but right now that > > > looks like a longer learning curve/ time sink. =A0(strange as that ma=y> > > sound.) > > > >> I m just trying to be helpful and I wish you the best of luck. > > > > Thanks again. =A0At the moment I'm just going to order some VCO's fro=m> > > minicirciuts... (throw some money at the problem.) and see what the > > > output looks like. =A0I'll also push forward on the triangle wave/ si=ne> > > shaper idea. > > > > This is a nice app note, > > >http://www.national.com/an/AN/AN-263.pdf > > > > George H. > > > >> Btw, you do want to go with frequencies up over 10MHz. =A0Get far aw=ay> > >> from your baseband, just makes the IF filtering all that much > > >> easier.- Hide quoted text - > > > >> - Show quoted text - > > > As I posted to the sample-hold thread by mistake: > > > Using a CD4017 and some resistors will get rid of all harmonics up to > > the ninth, so a fixed LPF will make a nice sine wave with 3:1 tunabilit=y.> > > Cheers > > > Phil Hobbs > > > -- > > Dr Philip C D Hobbs > > Principal Consultant > > ElectroOptical Innovations LLC > > Optics, Electro-optics, Photonics, Analog Electronics > > > 160 North State Road #203 > > Briarcliff Manor NY 10510 > > 845-480-2058 > > > hobbs at electrooptical dot nethttp://electrooptical.net-Hide quoted te=xt -> > > - Show quoted text - > > Hi Phil, =A0CD4017? =A0A decade counter. =A0Summing different 'fractions' > into an opamp to get a 'stepped' sine wave? > Color me confused. > > George H.It's the same as what I posted, except Phil's gone one better and merged the counter and decoder into one device: CD4017 .-------. 10x | | clk --|> 0 |---[R0]---. | | | | 1 |---[R1]---+ .-----. | | | | | | 2 |---[R2]---+---| LPF |----- | | | | | | 3 |---[R3]---+ '-----' | | | | 4 |---[R4]---+ ~~~ ~~~ ~~~ ~~~ ~~~ | | '-------' where energizing R0-9 in succession produces a full sine-wave cycle. I was going to suggest generating a quarter or half cycle with the resistors, then using analog steering and extra logic to invert and reverse as needed. That boosts resolution, but Phil's sure is simpler. -- Cheers, James Arthur
Reply by ●September 30, 20112011-09-30
On Sep 30, 8:57=A0am, George Herold <gher...@teachspin.com> wrote:> On Sep 29, 2:25=A0pm, me0...@yahoo.com wrote: > > > > > > > On Sep 29, 9:11=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Sep 28, 5:38=A0pm, Bill Sloman <bill.slo...@ieee.org> wrote: > > > > > On Sep 28, 9:41=A0pm, George Herold <gher...@teachspin.com> wrote: > > > > > > On Sep 28, 1:41=A0pm, "Michael A. Terrell" <mike.terr...@earthlin=k.net>> > > > > wrote: > > > > > > > George Herold wrote: > > > > > > > > Yeah DDS from a micro looks like the 'best' path. =A0It's jus=t outside> > > > > > > my present comfort zone and so hard to predict how long it wi=ll> > > > > > > take. > > > > > > > =A0 =A0You can get a "AD9850 Module DDS Signal Generator with C=ircuit> > > > > > Diagram" in ebay for about $13 and demo software on the Analog =Devices> > > > > > website. =A0There is also VB source code & 80*51 source code av=ailible for> > > > > > free. > > > > > > > =A0 =A0I just bought a couple for a project I'm working on. > > > > > > > -- > > > > > > You can't have a sense of humor, if you have no sense. > > > > > > Thanks Michael, =A0there's so many DDS chips. =A0Which ones will =still be> > > > > around in ten years? > > > > > The first mention of the AD9850 I can find here dates back to 2000,=so> > > > it has been around for more than ten years already - always a good > > > > sign - and I think that it had been around for a while then. IIRR i=t> > > > was the first of Analog Devices DDS chips, and it seems to have bee=n> > > > designed into a lot of applications, so it may be around for a whil=e> > > > yet. > > > > > -- > > > > Bill Sloman, Nijmegen- Hide quoted text - > > > > > - Show quoted text - > > > > Thanks Bill, that's good to know. > > > > George H.- Hide quoted text - > > > > - Show quoted text - > > > George, > > > What kind of tuning resolution do you need?- Hide quoted text - > > > - Show quoted text - > > Hi MeO, =A0The product will be doing all sorts of Fourier analysis. =A0At > the moment I think the reason for the VCO is only to look at > sidebands*. =A0And mostly sidebnads at a high modulation index... So I'd > like to modulate it with a (say) 1kHz sine wave and see sidebands out > to maybe the 7th to 10th harmonic. =A0I'm not sure how to turn this into > a resolution spec. > > George H. > > *It would be nice if we had some other 'physics' to do with the VCO. > Then I might have some 'real' specs.- Hide quoted text - > > - Show quoted text -George, So do I understand correctly, you need a variable sine source that tunes in frequency from 30Khz to 100KHz; this will serve as the LO in a system that generates a modulated output? So my question re resolution, how course a step size do you need the variable sine source to move in? Is it 1Hz, 100Hz, 1KHz, 10KHz, etc? Then of course the next question is, what is your requirement on frequency accuracy? For example say you want to set the system to 30KHz, if it=92s off by 60KHz is that an issue? If it wonders around by +/- 30KHz once set, is that an issue? Regards
Reply by ●September 30, 20112011-09-30
On Sep 30, 12:55=A0pm, dagmargoodb...@yahoo.com wrote:> On Sep 30, 11:01=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Sep 29, 4:05=A0pm, Phil Hobbs > > > <pcdhSpamMeSensel...@electrooptical.net> wrote: > > > On 09/29/2011 12:11 PM, George Herold wrote: > > > > > On Sep 28, 4:33 pm, me0...@yahoo.com wrote: > > > >> On Sep 28, 12:34 pm, George Herold<gher...@teachspin.com> =A0wrote=:> > > > >>> On Sep 28, 1:38 pm, Tim Wescott<t...@seemywebsite.com> =A0wrote: > > > > > <big snip> > > > >>> - Show quoted text - > > > > >> Hey George, > > > > >> Here s some more food for thought re the downconverter approach: > > > > > Hi MeO > > > > >> (you ve never said what you re looking for in Frequency stability,=but> > > >> I m assuming you want accuracy set by your XOSC and phase noise is > > > >> really not an issue) > > > > > Hmm, this is a small part of a new project. =A0I'm still trying to =get a> > > > handle on the specs I need. > > > > >> If you ve never done this before I would discourage you: > > > > >> 1) =A0 =A0 =A0 Unless you ve got the time to put into the learning=curve, not> > > >> only RF but the Freq Synth part > > > >> 2) =A0 =A0 =A0You have access to a decent SA or FFT analyzer that =can cover your> > > >> frequency of interest > > > >> 3) =A0 =A0 =A0A low frequency network analyzer would also make the=job a lot> > > >> easier > > > > > Well, an RF amplifier design ~20 years ago. =A0(would have been nic=e to> > > > have a spectrum analyzer at the time, I had some ring down issues i=n> > > > one of the amp stages.) =A0The only RF recently is a few watt oscil=lator> > > > for a Rubidium discharge lamp. =A0(Where frequency stability is not=much> > > > of an issue.) =A0I've got a 'new' SRS770 spectrum analyzer, (DC-100=kHz)> > > > which should tell me all I need to know about what's happening afte=r> > > > the mixer. > > > > >> You ve got another potential problem when you attempt this kind of > > > >> frequency translation. =A0The low Q VCO is going to have a tendenc=y to> > > >> be pulled around by the high Q XOSC. =A0They sniff each other when > > > >> they get close frequency wise. > > > > > Hmm a bit of padding should take care of that... I'll just burn > > > > power! > > > > >> So you have to make sure your system has enough isolation between =the> > > >> two oscillators. =A0You need to take into account things like LO t=o RF> > > >> isolation when looking at the mixer. =A0In S parameter terms it wi=ll> > > >> be the S12 term of the VCO chain. > > > > >> Again I will state, I really believe your VCO will have to be phas=ed> > > >> locked. =A0Otherwise it ll be hit and miss when trying to set it s > > > >> freq. =A0Each one of those gain curves will be slightly different =from> > > >> part to part. > > > > >> I don t mean to discourage you. =A0In fact, for somebody that does=synth> > > >> design this is pretty trivial. > > > > >> But for a first timer it will be daunting, and could really end up > > > >> being a big waste of time. =A0The digital approach is just a matte=r of> > > >> ramping up and not equipment intensive. =A0And software is compara=tively> > > >> easier to change then hardware. > > > > > Thanks, =A0I'd like to do a DDS design sometime, but right now that > > > > looks like a longer learning curve/ time sink. =A0(strange as that =may> > > > sound.) > > > > >> I m just trying to be helpful and I wish you the best of luck. > > > > > Thanks again. =A0At the moment I'm just going to order some VCO's f=rom> > > > minicirciuts... (throw some money at the problem.) and see what the > > > > output looks like. =A0I'll also push forward on the triangle wave/ =sine> > > > shaper idea. > > > > > This is a nice app note, > > > >http://www.national.com/an/AN/AN-263.pdf > > > > > George H. > > > > >> Btw, you do want to go with frequencies up over 10MHz. =A0Get far =away> > > >> from your baseband, just makes the IF filtering all that much > > > >> easier.- Hide quoted text - > > > > >> - Show quoted text - > > > > As I posted to the sample-hold thread by mistake: > > > > Using a CD4017 and some resistors will get rid of all harmonics up to > > > the ninth, so a fixed LPF will make a nice sine wave with 3:1 tunabil=ity.> > > > Cheers > > > > Phil Hobbs > > > > -- > > > Dr Philip C D Hobbs > > > Principal Consultant > > > ElectroOptical Innovations LLC > > > Optics, Electro-optics, Photonics, Analog Electronics > > > > 160 North State Road #203 > > > Briarcliff Manor NY 10510 > > > 845-480-2058 > > > > hobbs at electrooptical dot nethttp://electrooptical.net-Hidequoted t=ext -> > > > - Show quoted text - > > > Hi Phil, =A0CD4017? =A0A decade counter. =A0Summing different 'fraction=s'> > into an opamp to get a 'stepped' sine wave? > > Color me confused. > > > George H. > > It's the same as what I posted, except Phil's gone one better and > merged the counter and decoder into one device: > > =A0 =A0 =A0 =A0 CD4017 > =A0 =A0 =A0 =A0.-------. > 10x =A0 =A0| =A0 =A0 =A0 | > =A0clk --|> =A0 =A00 |---[R0]---. > =A0 =A0 =A0 =A0| =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0| =A0 =A0 1 |---[R1]---+ =A0 .-----. > =A0 =A0 =A0 =A0| =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0| =A0 | =A0 =A0 | > =A0 =A0 =A0 =A0| =A0 =A0 2 |---[R2]---+---| LPF |----- > =A0 =A0 =A0 =A0| =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0| =A0 | =A0 =A0 | > =A0 =A0 =A0 =A0| =A0 =A0 3 |---[R3]---+ =A0 '-----' > =A0 =A0 =A0 =A0| =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0| =A0 =A0 4 |---[R4]---+ > =A0 =A0 =A0 ~~~ =A0 =A0 ~~~ =A0 =A0 =A0 =A0~~~ > =A0 =A0 =A0 ~~~ =A0 =A0 ~~~ > =A0 =A0 =A0 =A0| =A0 =A0 =A0 | > =A0 =A0 =A0 =A0'-------' > > where energizing R0-9 in succession produces a full sine-wave cycle. > > I was going to suggest generating a quarter or half cycle with the > resistors, then using analog steering and extra logic to invert and > reverse as needed. =A0That boosts resolution, but Phil's sure is > simpler. > > -- > Cheers, > James Arthur- Hide quoted text - > > - Show quoted text -Ahh OK, I think I see. I've got to make some of the numbers give a negative voltage... or else let the 'sine wave' have a DC offset and AC couple it. All fun stuff. Thanks george H.
Reply by ●September 30, 20112011-09-30
On Sep 30, 1:10=A0pm, me0...@yahoo.com wrote:> On Sep 30, 8:57=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Sep 29, 2:25=A0pm, me0...@yahoo.com wrote: > > > > On Sep 29, 9:11=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > On Sep 28, 5:38=A0pm, Bill Sloman <bill.slo...@ieee.org> wrote: > > > > > > On Sep 28, 9:41=A0pm, George Herold <gher...@teachspin.com> wrote=:> > > > > > > On Sep 28, 1:41=A0pm, "Michael A. Terrell" <mike.terr...@earthl=ink.net>> > > > > > wrote: > > > > > > > > George Herold wrote: > > > > > > > > > Yeah DDS from a micro looks like the 'best' path. =A0It's j=ust outside> > > > > > > > my present comfort zone and so hard to predict how long it =will> > > > > > > > take. > > > > > > > > =A0 =A0You can get a "AD9850 Module DDS Signal Generator with=Circuit> > > > > > > Diagram" in ebay for about $13 and demo software on the Analo=g Devices> > > > > > > website. =A0There is also VB source code & 80*51 source code =availible for> > > > > > > free. > > > > > > > > =A0 =A0I just bought a couple for a project I'm working on. > > > > > > > > -- > > > > > > > You can't have a sense of humor, if you have no sense. > > > > > > > Thanks Michael, =A0there's so many DDS chips. =A0Which ones wil=l still be> > > > > > around in ten years? > > > > > > The first mention of the AD9850 I can find here dates back to 200=0, so> > > > > it has been around for more than ten years already - always a goo=d> > > > > sign - and I think that it had been around for a while then. IIRR=it> > > > > was the first of Analog Devices DDS chips, and it seems to have b=een> > > > > designed into a lot of applications, so it may be around for a wh=ile> > > > > yet. > > > > > > -- > > > > > Bill Sloman, Nijmegen- Hide quoted text - > > > > > > - Show quoted text - > > > > > Thanks Bill, that's good to know. > > > > > George H.- Hide quoted text - > > > > > - Show quoted text - > > > > George, > > > > What kind of tuning resolution do you need?- Hide quoted text - > > > > - Show quoted text - > > > Hi MeO, =A0The product will be doing all sorts of Fourier analysis. =A0=At> > the moment I think the reason for the VCO is only to look at > > sidebands*. =A0And mostly sidebnads at a high modulation index... So I'=d> > like to modulate it with a (say) 1kHz sine wave and see sidebands out > > to maybe the 7th to 10th harmonic. =A0I'm not sure how to turn this int=o> > a resolution spec. > > > George H. > > > *It would be nice if we had some other 'physics' to do with the VCO. > > Then I might have some 'real' specs.- Hide quoted text - > > > - Show quoted text - > > George, > > So do I understand correctly, you need a variable sine source that > tunes in frequency from 30Khz to 100KHz; this will serve as the LO in > a system that generates a modulated output? > > So my question re resolution, how course a step size do you need the > variable sine source to move in? =A0Is it 1Hz, 100Hz, 1KHz, 10KHz, etc? > > Then of course the next question is, what is your requirement on > frequency accuracy? =A0For example say you want to set the system to > 30KHz, if it=92s off by 60KHz is that an issue? =A0If it wonders around b=y> +/- 30KHz once set, is that an issue? > > Regards- Hide quoted text - > > - Show quoted text -Hey MeO, thanks for all your effort here! (I'm feeling guilty, wasting too much of everyones time already.) I've got a minicircuits order in, and I'll play around with the pieces and report back. After that I'll have a better idea of how this approach will work. George H.
Reply by ●September 30, 20112011-09-30
On Sep 30, 10:32=A0am, George Herold <gher...@teachspin.com> wrote:> On Sep 30, 1:10=A0pm, me0...@yahoo.com wrote: > > > > > > > On Sep 30, 8:57=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Sep 29, 2:25=A0pm, me0...@yahoo.com wrote: > > > > > On Sep 29, 9:11=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > On Sep 28, 5:38=A0pm, Bill Sloman <bill.slo...@ieee.org> wrote: > > > > > > > On Sep 28, 9:41=A0pm, George Herold <gher...@teachspin.com> wro=te:> > > > > > > > On Sep 28, 1:41=A0pm, "Michael A. Terrell" <mike.terr...@eart=hlink.net>> > > > > > > wrote: > > > > > > > > > George Herold wrote: > > > > > > > > > > Yeah DDS from a micro looks like the 'best' path. =A0It's=just outside> > > > > > > > > my present comfort zone and so hard to predict how long i=t will> > > > > > > > > take. > > > > > > > > > =A0 =A0You can get a "AD9850 Module DDS Signal Generator wi=th Circuit> > > > > > > > Diagram" in ebay for about $13 and demo software on the Ana=log Devices> > > > > > > > website. =A0There is also VB source code & 80*51 source cod=e availible for> > > > > > > > free. > > > > > > > > > =A0 =A0I just bought a couple for a project I'm working on. > > > > > > > > > -- > > > > > > > > You can't have a sense of humor, if you have no sense. > > > > > > > > Thanks Michael, =A0there's so many DDS chips. =A0Which ones w=ill still be> > > > > > > around in ten years? > > > > > > > The first mention of the AD9850 I can find here dates back to 2=000, so> > > > > > it has been around for more than ten years already - always a g=ood> > > > > > sign - and I think that it had been around for a while then. II=RR it> > > > > > was the first of Analog Devices DDS chips, and it seems to have=been> > > > > > designed into a lot of applications, so it may be around for a =while> > > > > > yet. > > > > > > > -- > > > > > > Bill Sloman, Nijmegen- Hide quoted text - > > > > > > > - Show quoted text - > > > > > > Thanks Bill, that's good to know. > > > > > > George H.- Hide quoted text - > > > > > > - Show quoted text - > > > > > George, > > > > > What kind of tuning resolution do you need?- Hide quoted text - > > > > > - Show quoted text - > > > > Hi MeO, =A0The product will be doing all sorts of Fourier analysis. ==A0At> > > the moment I think the reason for the VCO is only to look at > > > sidebands*. =A0And mostly sidebnads at a high modulation index... So =I'd> > > like to modulate it with a (say) 1kHz sine wave and see sidebands out > > > to maybe the 7th to 10th harmonic. =A0I'm not sure how to turn this i=nto> > > a resolution spec. > > > > George H. > > > > *It would be nice if we had some other 'physics' to do with the VCO. > > > Then I might have some 'real' specs.- Hide quoted text - > > > > - Show quoted text - > > > George, > > > So do I understand correctly, you need a variable sine source that > > tunes in frequency from 30Khz to 100KHz; this will serve as the LO in > > a system that generates a modulated output? > > > So my question re resolution, how course a step size do you need the > > variable sine source to move in? =A0Is it 1Hz, 100Hz, 1KHz, 10KHz, etc? > > > Then of course the next question is, what is your requirement on > > frequency accuracy? =A0For example say you want to set the system to > > 30KHz, if it=92s off by 60KHz is that an issue? =A0If it wonders around=by> > +/- 30KHz once set, is that an issue? > > > Regards- Hide quoted text - > > > - Show quoted text - > > Hey MeO, thanks for all your effort here! =A0(I'm feeling guilty, > wasting too much of everyones time already.) =A0I've got a minicircuits > order in, and I'll play around with the pieces and report back. =A0After > that I'll have a better idea of how this approach will work. > > George H.- Hide quoted text - > > - Show quoted text -Good luck George, I won't beat a dead horse, but the DDS really sounds like it was designed for your app. Have a look at there app notes if you already haven't. Depending on the part, great freq resolution, modulation capability and crystal stability. Regards
Reply by ●September 30, 20112011-09-30
On Fri, 30 Sep 2011 09:08:06 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Sep 29, 7:25�pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My- >Web-Site.com> wrote: >> On Thu, 29 Sep 2011 12:40:32 -0500, Frnak McKenney >> >> >> >> >> >> <fr...@far.from.the.madding.crowd.com> wrote: >> >On Tue, 27 Sep 2011 12:44:44 -0700 (PDT), George Herold <gher...@teachspin.com> wrote: >> >> On Sep 27, 2:17 pm, Tim Wescott <t...@seemywebsite.com> wrote: >> >>> On Tue, 27 Sep 2011 09:54:36 -0700, George Herold wrote: >> >> >>> > 30kHz to 100kHz VCO with sine wave output. >> >> > � [...] >> >> >> Hi Tim, �I've got a spice simulation with just diode limiting for the >> >> varible gain. �~1.2 Vp-p on the output. �I couldn't find any varactors >> >> in LTspice so I just used a diode and added some more C in parallel. >> >> >George, >> >> >You may have already achieved a useful solution, but I did run >> >across a numnber of potential models using the following search >> >string: >> >> > �+spice|ltspice +model varactor|vvc >> >> >including these: >> >> > �Varactor SPICE Models for RF VCO Applications - Skyworks >> > �http://www.skyworksinc.com/uploads/documents/200315B.pdf >> >> > �Spice Models for Aeroflex / Metelics GaAs Hyperabrupt Varactor >> > �http://www.aeroflex.com/ams/Metelics/pdfiles/MGV_spice_models.pdf >> >> >and Infineon has some spice models for (e.g.) its BB535 varactor. >> >Got to: >> >> > �http://http://www.infineon.com/ >> >> >and search for BB535. >> >> >Hope one of these helps. >> >> >Frank McKenney >> >-- >> > �"Expecting the world to treat you fairly because you are good is >> > � like expecting the bull not to charge because you are a >> > � vegetarian." � � � � � � �-- Dennis Wholey >> >> Do it with the exact data... >> >> www.analog-innovations.com/VVC.zip >> >> � � � � � � � � � � � � � � � � � � � �...Jim Thompson >> -- >> � � � � � � � � � [On the Road, in New York] >> >> | 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 athttp://www.analog-innovations.com| � �1962 � � | >> >> I love to cook with wine. � � Sometimes I even put it in the food.- Hide quoted text - >> >> - Show quoted text - > >Thanks Jim, I saved it. I've got so many ways to 'skin this cat' >now. I don't think that I'll be using a varactor. (at least for the >first try.) > >George H.Voltage tunable makes it tricky. Can you use range switching and a FET as a variable resistor? ...Jim Thompson -- [On the Road, in New York] | 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 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●September 30, 20112011-09-30
On 09/30/2011 12:01 PM, George Herold wrote:> On Sep 29, 4:05 pm, Phil Hobbs > <pcdhSpamMeSensel...@electrooptical.net> wrote: >> On 09/29/2011 12:11 PM, George Herold wrote: >> >> >> >> >> >>> On Sep 28, 4:33 pm, me0...@yahoo.com wrote: >>>> On Sep 28, 12:34 pm, George Herold<gher...@teachspin.com> wrote: >> >>>>> On Sep 28, 1:38 pm, Tim Wescott<t...@seemywebsite.com> wrote: >> >>> <big snip> >>>>> - Show quoted text - >> >>>> Hey George, >> >>>> Here s some more food for thought re the downconverter approach: >> >>> Hi MeO >> >>>> (you ve never said what you re looking for in Frequency stability, but >>>> I m assuming you want accuracy set by your XOSC and phase noise is >>>> really not an issue) >> >>> Hmm, this is a small part of a new project. I'm still trying to get a >>> handle on the specs I need. >> >>>> If you ve never done this before I would discourage you: >> >>>> 1) Unless you ve got the time to put into the learning curve, not >>>> only RF but the Freq Synth part >>>> 2) You have access to a decent SA or FFT analyzer that can cover your >>>> frequency of interest >>>> 3) A low frequency network analyzer would also make the job a lot >>>> easier >> >>> Well, an RF amplifier design ~20 years ago. (would have been nice to >>> have a spectrum analyzer at the time, I had some ring down issues in >>> one of the amp stages.) The only RF recently is a few watt oscillator >>> for a Rubidium discharge lamp. (Where frequency stability is not much >>> of an issue.) I've got a 'new' SRS770 spectrum analyzer, (DC-100kHz) >>> which should tell me all I need to know about what's happening after >>> the mixer. >> >>>> You ve got another potential problem when you attempt this kind of >>>> frequency translation. The low Q VCO is going to have a tendency to >>>> be pulled around by the high Q XOSC. They sniff each other when >>>> they get close frequency wise. >> >>> Hmm a bit of padding should take care of that... I'll just burn >>> power! >> >>>> So you have to make sure your system has enough isolation between the >>>> two oscillators. You need to take into account things like LO to RF >>>> isolation when looking at the mixer. In S parameter terms it will >>>> be the S12 term of the VCO chain. >> >>>> Again I will state, I really believe your VCO will have to be phased >>>> locked. Otherwise it ll be hit and miss when trying to set it s >>>> freq. Each one of those gain curves will be slightly different from >>>> part to part. >> >>>> I don t mean to discourage you. In fact, for somebody that does synth >>>> design this is pretty trivial. >> >>>> But for a first timer it will be daunting, and could really end up >>>> being a big waste of time. The digital approach is just a matter of >>>> ramping up and not equipment intensive. And software is comparatively >>>> easier to change then hardware. >> >>> Thanks, I'd like to do a DDS design sometime, but right now that >>> looks like a longer learning curve/ time sink. (strange as that may >>> sound.) >> >>>> I m just trying to be helpful and I wish you the best of luck. >> >>> Thanks again. At the moment I'm just going to order some VCO's from >>> minicirciuts... (throw some money at the problem.) and see what the >>> output looks like. I'll also push forward on the triangle wave/ sine >>> shaper idea. >> >>> This is a nice app note, >>> http://www.national.com/an/AN/AN-263.pdf >> >>> George H. >> >>>> Btw, you do want to go with frequencies up over 10MHz. Get far away >>>> from your baseband, just makes the IF filtering all that much >>>> easier.- Hide quoted text - >> >>>> - Show quoted text - >> >> As I posted to the sample-hold thread by mistake: >> >> Using a CD4017 and some resistors will get rid of all harmonics up to >> the ninth, so a fixed LPF will make a nice sine wave with 3:1 tunability. >> >> Cheers >> >> Phil Hobbs >> >> -- >> Dr Philip C D Hobbs >> Principal Consultant >> ElectroOptical Innovations LLC >> Optics, Electro-optics, Photonics, Analog Electronics >> >> 160 North State Road #203 >> Briarcliff Manor NY 10510 >> 845-480-2058 >> >> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text - >> >> - Show quoted text - > > Hi Phil, CD4017? A decade counter. Summing different 'fractions' > into an opamp to get a 'stepped' sine wave? > Color me confused. > > George H. >It's not just a decade counter--it's a decade counter _with_one-of-10_outputs_--the poor man's sequence generator. Wire the outputs together via weighted resistors. You have 10 samples per cycle, so you can get rid of the second through ninth harmonics. If you don't mind adding a couple of open-collector or tri-state buffer parts(*), the resistors just go as R_N = 1/sin((N+1/2) pi/10). Pretty simple. If you want elegance, you can save the buffers and just form a weighted sum of all of the conductances--the math isn't hard, because it's one-of-10. 4017s are wonderful for bodging together some little piece of test gear that needs good timing accuracy. Cheers Phil Hobbs (*) You know the trick for getting open-collector behaviour out of tri-state parts, right? You ground the inputs, and put the logic signal into tri-state line. You don't get as many per package, but they come in faster logic families. -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
