Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:> On 31.10.18 07:57, Steve Wilson wrote: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 10/31/18 12:52 AM, 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. >> >>> For bandwidths that wide, I'd be looking at a delay discriminator. In >>> the lab that would be a coax cable and a MCL mixer. >> >>> Cheers >> >>> Phil Hobbs >> >> How do you get down to DC with a delay discriminator? > > > A ring mixer can go down to DC on its low-frequency port. > When the delay is 90 degrees, the output will be zero.Doesn't help. You need a reference frequency which doesn't exist on a delay discriminator.
wideband FM demodulator
Started by ●October 31, 2018
Reply by ●October 31, 20182018-10-31
Reply by ●October 31, 20182018-10-31
On 31.10.18 10:33, Steve Wilson wrote:> Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote: > >> On 31.10.18 07:57, Steve Wilson wrote: >>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 10/31/18 12:52 AM, 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. >>> >>>> For bandwidths that wide, I'd be looking at a delay discriminator. In >>>> the lab that would be a coax cable and a MCL mixer. >>> >>>> Cheers >>> >>>> Phil Hobbs >>> >>> How do you get down to DC with a delay discriminator? >> >> >> A ring mixer can go down to DC on its low-frequency port. >> When the delay is 90 degrees, the output will be zero. > > Doesn't help. You need a reference frequency which doesn't exist on a delay > discriminator.The reference is in the delay. You take two copies of the amplitude-limited input signal, delay one of them and mix together. The low-passed mixer output is zero on the ferquency where the line delay is 90 degrees. -- -TV
Reply by ●October 31, 20182018-10-31
On Wednesday, October 31, 2018 at 1:57:23 AM UTC-4, Steve Wilson wrote:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > On 10/31/18 12:52 AM, 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. > > > For bandwidths that wide, I'd be looking at a delay discriminator. In > > the lab that would be a coax cable and a MCL mixer. > > > Cheers > > > Phil Hobbs > > How do you get down to DC with a delay discriminator?Never mind. At 500 Mhz, a 500 ps delay would provide the necessary phase shift for a quadrature demodulator.
Reply by ●October 31, 20182018-10-31
On Wednesday, October 31, 2018 at 4:23:21 AM UTC-4, Tauno Voipio wrote:> On 31.10.18 07:57, Steve Wilson wrote: > > Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > >> On 10/31/18 12:52 AM, 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. > > > >> For bandwidths that wide, I'd be looking at a delay discriminator. In > >> the lab that would be a coax cable and a MCL mixer. > > > >> Cheers > > > >> Phil Hobbs > > > > How do you get down to DC with a delay discriminator? > > > A ring mixer can go down to DC on its low-frequency port. > When the delay is 90 degrees, the output will be zero. > > -- > > -TVYes. At 500 Mhz, a 500 ps delay would provide the necessary phase shift for a quadrature demodulator.
Reply by ●October 31, 20182018-10-31
On Wednesday, October 31, 2018 at 5:04:12 AM UTC-4, Tauno Voipio wrote:> On 31.10.18 10:33, Steve Wilson wrote: > > Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote: > > > >> On 31.10.18 07:57, Steve Wilson wrote: > >>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >>> > >>>> On 10/31/18 12:52 AM, 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. > >>> > >>>> For bandwidths that wide, I'd be looking at a delay discriminator. In > >>>> the lab that would be a coax cable and a MCL mixer. > >>> > >>>> Cheers > >>> > >>>> Phil Hobbs > >>> > >>> How do you get down to DC with a delay discriminator? > >> > >> > >> A ring mixer can go down to DC on its low-frequency port. > >> When the delay is 90 degrees, the output will be zero. > > > > Doesn't help. You need a reference frequency which doesn't exist on a delay > > discriminator. > > > The reference is in the delay. > > You take two copies of the amplitude-limited input signal, > delay one of them and mix together. The low-passed mixer > output is zero on the ferquency where the line delay is 90 degrees. > > -- > > -TVYes. At 500 Mhz, a 500 ps delay would provide the necessary phase shift for a quadrature demodulator.
Reply by ●October 31, 20182018-10-31
On Wednesday, October 31, 2018 at 4:21:31 AM UTC-4, Steve Wilson wrote:> 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. > > Probably a Tek TPS2000. I would expect a pll demodulator. Not hard to do with > today's ic's.Never mind. At 500 Mhz, a 500 ps delay would provide the necessary phase shift for a quadrature demodulator.
Reply by ●October 31, 20182018-10-31
On Wednesday, October 31, 2018 at 4:21:31 AM UTC-4, Steve Wilson wrote:> 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. > > Probably a Tek TPS2000. I would expect a pll demodulator. Not hard to do with > today's ic's.Nah. A 1/4 wave delay is much simpler and has wider bandwidth. At 500 MHz, a 500 ps delay will provide the necessary phase shift for a quadrature demodulator. You need a fairly wide frequency modulation for reasonable demodulated signal amplitude. I'm trying to decide if that will produce significant distortion but don't have time to model it in LTspice.
Reply by ●October 31, 20182018-10-31
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?An other way, using same one shot, is if you have say 1GHz, and a sweep from 0.9 to 1.1 GHz, mix it down with 800 MHz, lowpass 200 MHz (only want the diff, not the 1.9 GHz) Now you have a sweep from 100 MHz to 200 MHz. Trigger a fixed time oneshot on each zero crossing, lowpass <= 50 MHz, now you have a 1 to 2 voltage change. Its linear Its simple It is not suitable for a radio link, bit works fine on fixed wire.
Reply by ●October 31, 20182018-10-31
On 10/31/18 8:38 AM, 698839253X6D445TD@nospam.org wrote:> 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? > > An other way, using same one shot, is if you have say 1GHz, and a > sweep from 0.9 to 1.1 GHz, mix it down with 800 MHz, lowpass 200 MHz > (only want the diff, not the 1.9 GHz) Now you have a sweep from 100 > MHz to 200 MHz. Trigger a fixed time oneshot on each zero crossing, > lowpass <= 50 MHz, now you have a 1 to 2 voltage change. Its linear > Its simpleIt's drifty and super noisy Its sensitivity is harder to predict It requires way more circuitry> It is not suitable for a radio link, bit works fine on fixed wire.For sufficiently permissive definitions of 'fine'. ;) 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 http://hobbs-eo.com
Reply by ●October 31, 20182018-10-31
On Wed, 31 Oct 2018 05:45:35 -0000 (UTC), Jasen Betts <jasen@xnet.co.nz> wrote:>On 2018-10-31, 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. > >SDREasy for you to say! -- John Larkin Highland Technology, Inc lunatic fringe electronics
