On 11/01/2018 01:44 AM, Steve Wilson wrote:> John Larkin <jjlarkin@highland_snip_technology.com> wrote: > >> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: > >>> John Larkin <jjlarkin@highlandtechnology.com> wrote: > >>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. > >>>> I can get the VCO. What's a good way to do the FM discriminator these >>>> days? > >>>> I could homebrew a quadrature detector, with some resonator and an XOR >>>> gate or a mixer, but there must be some easier way to do it. Not being >>>> an RF type, I'd appreciate suggestions. > >>> You have a scope with an isolated ground. Take it apart and find out how >>> it works. > >> There's probably a patent somewhere. > > If you understand patent claims, you can easily find a way around them. > There are probably many patents for transferring information across a > barrier. Even a slight difference constitutes a different invention. This > is how pharmaceutical companies get new patents on virtually identical > products. Your application is different, therefore most existing patents > won't apply.Careful with that advice. Patents are legal documents more than technical ones. What constitutes a sufficient difference to establish noninfringement depends on a lot more than the claims. Google "doctrine of equivalents" for instance.> >> But scopes don't need a lot of linearity or dynamic range. Most are >> barely 8 bit machines. They can, probably do, put a switchable >> attenuator ahead of the FM isolation link. > > True, but that has nothing to do with your application.I understood that to mean that a solution good enough for 7-8 bits wouldn't necessarily be good enough for John's. I'll have to do the math for the trig series and try out a linearized delay discriminator. I've been doing way too many BOMs and ECOs and stuff lately. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
wideband FM demodulator
Started by ●October 31, 2018
Reply by ●November 1, 20182018-11-01
Reply by ●November 1, 20182018-11-01
On Thu, 01 Nov 2018 07:20:33 -0700, Joerg <news@analogconsultants.com> wrote:>On 2018-10-31 22:44, Steve Wilson wrote: >> John Larkin <jjlarkin@highland_snip_technology.com> wrote: >> >>> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: >> >>>> John Larkin <jjlarkin@highlandtechnology.com> wrote: >> >>>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >>>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >> >>>>> I can get the VCO. What's a good way to do the FM discriminator these >>>>> days? >> >>>>> I could homebrew a quadrature detector, with some resonator and an XOR >>>>> gate or a mixer, but there must be some easier way to do it. Not being >>>>> an RF type, I'd appreciate suggestions. >> >>>> You have a scope with an isolated ground. Take it apart and find out how >>>> it works. >> > >Often that's just synchronous AM. Which may also be doable in John's >case but hard to say without knowing dynamic range specs and stuff.A target might be 50 to 100 MHz bandwidth and 75 dB dynamic range. The comm link will be fiber. If we go digital, we could digitize to 14 bits at around 300 MHz. With some carefully planned framing overhead, thet would fit into a 5 Gbit/sec fiber link.> > >>> There's probably a patent somewhere. >> >> If you understand patent claims, you can easily find a way around them. >> There are probably many patents for transferring information across a >> barrier. Even a slight difference constitutes a different invention. This >> is how pharmaceutical companies get new patents on virtually identical >> products. Your application is different, therefore most existing patents >> won't apply. >> > >Most patents these days are broad grab attempts along the lines of >"Let's throw all these spaghetti at the wall and see which ones stick". >It is assumed that litigation will weed out bad claims or maybe whole >patents. > > >>> But scopes don't need a lot of linearity or dynamic range. Most are >>> barely 8 bit machines. They can, probably do, put a switchable >>> attenuator ahead of the FM isolation link. >> >> True, but that has nothing to do with your application. >> > >I may be wrong but I doubt that they have an FM link.My Tek DPO2024 does, I think, use a roughly 3 GHz FM link for the channel and trigger isolation. Tek does have some products that use optical isolation. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 1, 20182018-11-01
On 10/31/2018 03:44 PM, Phil Hobbs wrote:> On 10/31/18 2:08 PM, John Larkin wrote: >> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: >> >>> John Larkin <jjlarkin@highlandtechnology.com> wrote: >>> >>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >>> >>>> I can get the VCO. What's a good way to do the FM discriminator these >>>> days? >>> >>>> I could homebrew a quadrature detector, with some resonator and an XOR >>>> gate or a mixer, but there must be some easier way to do it. Not being >>>> an RF type, I'd appreciate suggestions. >>> >>> You have a scope with an isolated ground. Take it apart and find out >>> how it >>> works. >>> >>> >> >> There's probably a patent somewhere. >> >> But scopes don't need a lot of linearity or dynamic range. Most are >> barely 8 bit machines. They can, probably do, put a switchable >> attenuator ahead of the FM isolation link. > > The dominant distortion of a delay discriminator running at constant > amplitude is cubic. That can be corrected using a second discriminator > with three times the delay, and adding something like 1/3! of its output > to the first one. (The trigonometric series isn't the same as the > Maclaurin series.) That would leave the dominant distortion as > fifth-order, which ought to be small enough to ignore.If you go as far as fifth-order, you can get the nonlinearity below 0.1% of reading in a fractional bandwidth of 65%. See https://electrooptical.net/static/oldsite/www/sed/DelayDiscrim.png and the circuit at <https://electrooptical.net/static/oldsite/www/sed/DelayDiscriminatorLinearizer.asc> Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Reply by ●November 1, 20182018-11-01
On Wed, 31 Oct 2018 14:36:20 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>onsdag den 31. oktober 2018 kl. 21.04.57 UTC+1 skrev John Larkin: >> On Wed, 31 Oct 2018 15:44:30 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> >On 10/31/18 2:08 PM, John Larkin wrote: >> >> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: >> >> >> >>> John Larkin <jjlarkin@highlandtechnology.com> wrote: >> >>> >> >>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >> >>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >> >>> >> >>>> I can get the VCO. What's a good way to do the FM discriminator these >> >>>> days? >> >>> >> >>>> I could homebrew a quadrature detector, with some resonator and an XOR >> >>>> gate or a mixer, but there must be some easier way to do it. Not being >> >>>> an RF type, I'd appreciate suggestions. >> >>> >> >>> You have a scope with an isolated ground. Take it apart and find out how it >> >>> works. >> >>> >> >>> >> >> >> >> There's probably a patent somewhere. >> >> >> >> But scopes don't need a lot of linearity or dynamic range. Most are >> >> barely 8 bit machines. They can, probably do, put a switchable >> >> attenuator ahead of the FM isolation link. >> > >> >The dominant distortion of a delay discriminator running at constant >> >amplitude is cubic. That can be corrected using a second discriminator >> >with three times the delay, and adding something like 1/3! of its output >> >to the first one. (The trigonometric series isn't the same as the >> >Maclaurin series.) That would leave the dominant distortion as >> >fifth-order, which ought to be small enough to ignore. >> > >> >Cheers >> > >> >Phil Hobbs >> >> There's a faction here that just wants to digitize the signal at 250 >> Ms/s and ship it as 8B10B serial data. Makes some sense. The ADC will >> cost $60 or so, > >how many bits?We'd need 14 to meet one customer's dynamic range spec. We have a nice 12 bit 250M ADC in stock. If we oversample a bunch, we could dither a bit and squeeze out a few more dBs. I could just buy a 310 MHz 14-bit ADC and pass along the cost. https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LTC2153IUJ-14-PBF/LTC2153IUJ-14-PBF-ND/3024843 Sampling at, say 300M, we could use 8B10B serial transmission at 6 Gbits/sec. Dang, all this digital stuff makes design boring. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 1, 20182018-11-01
Am 01.11.18 um 18:15 schrieb John Larkin:> On Wed, 31 Oct 2018 14:36:20 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > >> onsdag den 31. oktober 2018 kl. 21.04.57 UTC+1 skrev John Larkin: >>> On Wed, 31 Oct 2018 15:44:30 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 10/31/18 2:08 PM, John Larkin wrote: >>>>> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: >>>>> >>>>>> John Larkin <jjlarkin@highlandtechnology.com> wrote: >>>>>> >>>>>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >>>>>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >>>>>> >>>>>>> I can get the VCO. What's a good way to do the FM discriminator these >>>>>>> days? >>>>>> >>>>>>> I could homebrew a quadrature detector, with some resonator and an XOR >>>>>>> gate or a mixer, but there must be some easier way to do it. Not being >>>>>>> an RF type, I'd appreciate suggestions. >>>>>> >>>>>> You have a scope with an isolated ground. Take it apart and find out how it >>>>>> works. >>>>>> >>>>>> >>>>> >>>>> There's probably a patent somewhere. >>>>> >>>>> But scopes don't need a lot of linearity or dynamic range. Most are >>>>> barely 8 bit machines. They can, probably do, put a switchable >>>>> attenuator ahead of the FM isolation link. >>>> >>>> The dominant distortion of a delay discriminator running at constant >>>> amplitude is cubic. That can be corrected using a second discriminator >>>> with three times the delay, and adding something like 1/3! of its output >>>> to the first one. (The trigonometric series isn't the same as the >>>> Maclaurin series.) That would leave the dominant distortion as >>>> fifth-order, which ought to be small enough to ignore. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> There's a faction here that just wants to digitize the signal at 250 >>> Ms/s and ship it as 8B10B serial data. Makes some sense. The ADC will >>> cost $60 or so, >> >> how many bits? > > We'd need 14 to meet one customer's dynamic range spec. We have a nice > 12 bit 250M ADC in stock. If we oversample a bunch, we could dither a > bit and squeeze out a few more dBs. > > I could just buy a 310 MHz 14-bit ADC and pass along the cost. > > https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LTC2153IUJ-14-PBF/LTC2153IUJ-14-PBF-ND/3024843 > > Sampling at, say 300M, we could use 8B10B serial transmission at 6 > Gbits/sec. > > Dang, all this digital stuff makes design boring.AD9694. 4 ADCs 14 Bits/500MSPS each, JESD204B serializeres included. Up to 15 GBit/s per lane if wanted. That's where digital turns analog again. regards, Gerhard
Reply by ●November 1, 20182018-11-01
torsdag den 1. november 2018 kl. 18.15.39 UTC+1 skrev John Larkin:> On Wed, 31 Oct 2018 14:36:20 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > > >onsdag den 31. oktober 2018 kl. 21.04.57 UTC+1 skrev John Larkin: > >> On Wed, 31 Oct 2018 15:44:30 -0400, Phil Hobbs > >> <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> > >> >On 10/31/18 2:08 PM, John Larkin wrote: > >> >> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: > >> >> > >> >>> John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> >>> > >> >>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using > >> >>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. > >> >>> > >> >>>> I can get the VCO. What's a good way to do the FM discriminator these > >> >>>> days? > >> >>> > >> >>>> I could homebrew a quadrature detector, with some resonator and an XOR > >> >>>> gate or a mixer, but there must be some easier way to do it. Not being > >> >>>> an RF type, I'd appreciate suggestions. > >> >>> > >> >>> You have a scope with an isolated ground. Take it apart and find out how it > >> >>> works. > >> >>> > >> >>> > >> >> > >> >> There's probably a patent somewhere. > >> >> > >> >> But scopes don't need a lot of linearity or dynamic range. Most are > >> >> barely 8 bit machines. They can, probably do, put a switchable > >> >> attenuator ahead of the FM isolation link. > >> > > >> >The dominant distortion of a delay discriminator running at constant > >> >amplitude is cubic. That can be corrected using a second discriminator > >> >with three times the delay, and adding something like 1/3! of its output > >> >to the first one. (The trigonometric series isn't the same as the > >> >Maclaurin series.) That would leave the dominant distortion as > >> >fifth-order, which ought to be small enough to ignore. > >> > > >> >Cheers > >> > > >> >Phil Hobbs > >> > >> There's a faction here that just wants to digitize the signal at 250 > >> Ms/s and ship it as 8B10B serial data. Makes some sense. The ADC will > >> cost $60 or so, > > > >how many bits? > > We'd need 14 to meet one customer's dynamic range spec. We have a nice > 12 bit 250M ADC in stock. If we oversample a bunch, we could dither a > bit and squeeze out a few more dBs. > > I could just buy a 310 MHz 14-bit ADC and pass along the cost. > > https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LTC2153IUJ-14-PBF/LTC2153IUJ-14-PBF-ND/3024843 >HMCAD1520, ADS4129, ADS41B49 seems to be in the ballpark substantially cheaper
Reply by ●November 1, 20182018-11-01
On 2018-11-01 08:22, John Larkin wrote:> On Thu, 01 Nov 2018 07:20:33 -0700, Joerg <news@analogconsultants.com> > wrote: > >> On 2018-10-31 22:44, Steve Wilson wrote: >>> John Larkin <jjlarkin@highland_snip_technology.com> wrote: >>> >>>> On Wed, 31 Oct 2018 06:22:49 GMT, Steve Wilson <no@spam.com> wrote: >>> >>>>> John Larkin <jjlarkin@highlandtechnology.com> wrote: >>> >>>>>> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >>>>>> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >>> >>>>>> I can get the VCO. What's a good way to do the FM discriminator these >>>>>> days? >>> >>>>>> I could homebrew a quadrature detector, with some resonator and an XOR >>>>>> gate or a mixer, but there must be some easier way to do it. Not being >>>>>> an RF type, I'd appreciate suggestions. >>> >>>>> You have a scope with an isolated ground. Take it apart and find out how >>>>> it works. >>> >> >> Often that's just synchronous AM. Which may also be doable in John's >> case but hard to say without knowing dynamic range specs and stuff. > > A target might be 50 to 100 MHz bandwidth and 75 dB dynamic range. The > comm link will be fiber. >With that 75dB spec I'd use FM and maybe a delay line detector.> If we go digital, we could digitize to 14 bits at around 300 MHz. With > some carefully planned framing overhead, thet would fit into a 5 > Gbit/sec fiber link. >You could do that but it'll be much more hardware effort than FM.>> >> >>>> There's probably a patent somewhere. >>> >>> If you understand patent claims, you can easily find a way around them. >>> There are probably many patents for transferring information across a >>> barrier. Even a slight difference constitutes a different invention. This >>> is how pharmaceutical companies get new patents on virtually identical >>> products. Your application is different, therefore most existing patents >>> won't apply. >>> >> >> Most patents these days are broad grab attempts along the lines of >> "Let's throw all these spaghetti at the wall and see which ones stick". >> It is assumed that litigation will weed out bad claims or maybe whole >> patents. >> >> >>>> But scopes don't need a lot of linearity or dynamic range. Most are >>>> barely 8 bit machines. They can, probably do, put a switchable >>>> attenuator ahead of the FM isolation link. >>> >>> True, but that has nothing to do with your application. >>> >> >> I may be wrong but I doubt that they have an FM link. > > My Tek DPO2024 does, I think, use a roughly 3 GHz FM link for the > channel and trigger isolation. Tek does have some products that use > optical isolation. >They have nice iso scope and I could really use one right now. However, for just one job I can't justify spending the equivalent of a small car. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●November 1, 20182018-11-01
On Wednesday, October 31, 2018 at 12:52:08 AM UTC-4, John Larkin wrote:> We're thinking of sending a wideband (say, dc to 50 MHz) signal using > FM. The carrier could be in the 500 MHz to 1 GHz range maybe. > > I can get the VCO. What's a good way to do the FM discriminator these > days? > > I could homebrew a quadrature detector, with some resonator and an XOR > gate or a mixer, but there must be some easier way to do it. Not being > an RF type, I'd appreciate suggestions.7 bucks https://www.minicircuits.com/pdfs/QBA-07+.pdf> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Reply by ●November 1, 20182018-11-01
On Thu, 1 Nov 2018 12:25:10 -0700 (PDT), bloggs.fredbloggs.fred@gmail.com wrote:>On Wednesday, October 31, 2018 at 12:52:08 AM UTC-4, John Larkin wrote: >> We're thinking of sending a wideband (say, dc to 50 MHz) signal using >> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. >> >> I can get the VCO. What's a good way to do the FM discriminator these >> days? >> >> I could homebrew a quadrature detector, with some resonator and an XOR >> gate or a mixer, but there must be some easier way to do it. Not being >> an RF type, I'd appreciate suggestions. > >7 bucks https://www.minicircuits.com/pdfs/QBA-07+.pdfHow would I use that? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 1, 20182018-11-01
On Thursday, November 1, 2018 at 1:37:31 PM UTC-7, John Larkin wrote:> On Thu, 1 Nov 2018 12:25:10 -0700 (PDT), > bloggs.fredbloggs.fred@gmail.com wrote: > > >On Wednesday, October 31, 2018 at 12:52:08 AM UTC-4, John Larkin wrote: > >> We're thinking of sending a wideband (say, dc to 50 MHz) signal using > >> FM. The carrier could be in the 500 MHz to 1 GHz range maybe. > >> > >> I can get the VCO. What's a good way to do the FM discriminator these > >> days? > >> > >> I could homebrew a quadrature detector, with some resonator and an XOR > >> gate or a mixer, but there must be some easier way to do it. Not being > >> an RF type, I'd appreciate suggestions. > > > >7 bucks https://www.minicircuits.com/pdfs/QBA-07+.pdf > > How would I use that?That'd be your delay line, used with a mixer to recover the modulated signal. It'll work but I'd be surprised if it's very stable. For the case you're describing, straight FM isn't all that common. I used an MC13155D for something similar at one point but it's gone the way of the 12AX7 (oh, wait, you can still get those). I wonder if there's a QAM chipset available with similar bandwidth? Something comparable to a cable or DSL modem, but without all the DOCSIS baggage. -- john, KE5FX
