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Re: Low Frequency 3rd Overtone Crystal Osc

From rickman <gnuarm@gmail.com>
Newsgroups sci.electronics.design
Subject Re: Low Frequency 3rd Overtone Crystal Osc
Date 2017-03-15 12:44 -0400
Organization A noiseless patient Spider
Message-ID <oabqrl$32p$1@dont-email.me> (permalink)
References (14 earlier) <oa7smf$9h9$1@gonzo.alcatraz> <oa99iu$jse$1@dont-email.me> <oa9jmf$pou$1@dont-email.me> <oaa3ge$f2k$1@dont-email.me> <oaaugg$2rv$1@dont-email.me>

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On 3/15/2017 4:40 AM, Tauno Voipio wrote:
> On 15.3.17 02:59, rickman wrote:
>> On 3/14/2017 4:29 PM, Tauno Voipio wrote:
>>> On 14.3.17 19:37, rickman wrote:
>>>> On 3/14/2017 12:48 AM, Jasen Betts wrote:
>>>>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote:
>>>>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote:
>>>>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev
>>>>>>> upsid...@downunder.com:
>>>>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:
>>>>>>>>
>>>>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote:
>>>>>>>>>> On 3/11/2017 2:37 AM, piglet wrote:
>>>>>>>>>>> On 10/03/2017 01:55, rickman wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board.
>>>>>>>>>>>> 60 kHz is
>>>>>>>>>>>> what I am measuring.
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Just wonder if having a strong 120kHz presence is wise if
>>>>>>>>>>> trying to
>>>>>>>>>>> measure a low level 60kHz signal? Would it be better to have a
>>>>>>>>>>> more
>>>>>>>>>>> complex harmonic relationship between high level oscillator and
>>>>>>>>>>> low-level input?
>>>>>>>>>>
>>>>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it
>>>>>>>>>> getting
>>>>>>>>>> into the signal.  It gets sampled right back out perfectly.
>>>>>>>>>
>>>>>>>>> unless you have some way to synchronise your clock to the 60kHz,
>>>>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no
>>>>>>>>> signal
>>>>>>>>
>>>>>>>> Quadrature (I/Q) demodulation should solve this problem.
>>>>>>>>
>>>>>>>> If you can lock into th signal, quadrature locking of Q will ensure
>>>>>>>> that the I channel doesn't cancel the data.
>>>>>>>
>>>>>>> not surprising since IQ sampling is basically equivalent to
>>>>>>> sampling at
>>>>>>> twice the rate
>>>>>>
>>>>>> This part was resolved a long time ago.  That's why the sampling
>>>>>> will be
>>>>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz.
>>>>>> The multiplies are all 1, -1 and 0 so no actual multiplies.  Sum the
>>>>>> complex results over a time period and you get a *very* narrow band
>>>>>> filter with complex results giving both amplitude and relative phase.
>>>>>>
>>>>>> That's why I prefer a 120 or 240 kHz crystal.  We'll see what I
>>>>>> end up
>>>>>> with.
>>>>>
>>>>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm
>>>>>
>>>>> dunno if they can provide "samples", I guessing you don't want to
>>>>> buy a
>>>>> reel.
>>>>
>>>> I can get a reel from Digikey.
>>>>
>>>>
>>>>> Have you considered doing the SDR thing instead?
>>>>
> Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
> From: Tauno Voipio <tauno.voipio@notused.fi.invalid>
> Newsgroups: sci.electronics.design
> Subject: Re: Low Frequency 3rd Overtone Crystal Osc
> Date: Wed, 15 Mar 2017 10:40:27 +0200
> Organization: A noiseless patient Spider
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>
> On 15.3.17 02:59, rickman wrote:
>> On 3/14/2017 4:29 PM, Tauno Voipio wrote:
>>> On 14.3.17 19:37, rickman wrote:
>>>> On 3/14/2017 12:48 AM, Jasen Betts wrote:
>>>>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote:
>>>>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote:
>>>>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev
>>>>>>> upsid...@downunder.com:
>>>>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:
>>>>>>>>
>>>>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote:
>>>>>>>>>> On 3/11/2017 2:37 AM, piglet wrote:
>>>>>>>>>>> On 10/03/2017 01:55, rickman wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board.
>>>>>>>>>>>> 60 kHz is
>>>>>>>>>>>> what I am measuring.
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Just wonder if having a strong 120kHz presence is wise if
>>>>>>>>>>> trying to
>>>>>>>>>>> measure a low level 60kHz signal? Would it be better to have a
>>>>>>>>>>> more
>>>>>>>>>>> complex harmonic relationship between high level oscillator and
>>>>>>>>>>> low-level input?
>>>>>>>>>>
>>>>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it
>>>>>>>>>> getting
>>>>>>>>>> into the signal.  It gets sampled right back out perfectly.
>>>>>>>>>
>>>>>>>>> unless you have some way to synchronise your clock to the 60kHz,
>>>>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no
>>>>>>>>> signal
>>>>>>>>
>>>>>>>> Quadrature (I/Q) demodulation should solve this problem.
>>>>>>>>
>>>>>>>> If you can lock into th signal, quadrature locking of Q will ensure
>>>>>>>> that the I channel doesn't cancel the data.
>>>>>>>
>>>>>>> not surprising since IQ sampling is basically equivalent to
>>>>>>> sampling at
>>>>>>> twice the rate
>>>>>>
>>>>>> This part was resolved a long time ago.  That's why the sampling
>>>>>> will be
>>>>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz.
>>>>>> The multiplies are all 1, -1 and 0 so no actual multiplies.  Sum the
>>>>>> complex results over a time period and you get a *very* narrow band
>>>>>> filter with complex results giving both amplitude and relative phase.
>>>>>>
>>>>>> That's why I prefer a 120 or 240 kHz crystal.  We'll see what I
>>>>>> end up
>>>>>> with.
>>>>>
>>>>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm
>>>>>
>>>>> dunno if they can provide "samples", I guessing you don't want to
>>>>> buy a
>>>>> reel.
>>>>
>>>> I can get a reel from Digikey.
>>>>
>>>>
>>>>> Have you considered doing the SDR thing instead?
>>>>
>>>> Software defined radio?  So if this is a hard problem to solve, I
>>>> should
>>>> solve a different problem?
>>>
>>>
>>> Maybe meaning DDS?
>>>
>>> I just wonder why the OP asks for a third overtone oscillator
>>> for extremely low frequency (60 kHz) for a crystal.
>>
>> I wish to synchronously sample a 60 kHz signal at 240 kHz.  I can't find
>> either 120 or 240 kHz crystals.  I *can* find 40 kHz crystals which
>> would give me 120 kHz at the third overtone (or close to it).
>>
>> I've read enough about this to be thoroughly scared off the prospect and
>> am now looking at using a 32.768 kHz reference (which I need anyway) to
>> drive a frequency locked loop by tuning an LC oscillator.  It would have
>> an update rate on the order of 1 Hz, so the stability could be pretty
>> close to that of the 32.768 kHz reference.  In simulation the power
>> consumption can be pretty low.  I think I'm about ready to build one and
>> give it a try.
>
>
> This may be a heresy:
>
> There are plenty of small ARM Cortex-M chips with built-in
> counter-timers. Get one of them with a decent crystal (say in the range of
> 5 to 20 MHz) and divide from it with the built-in timer. The cost
> will be just some dollars for the components.
>
> A small Cortex evaluation unit can be had for some tens of dollars,
> and there are the crystal and board built-in, together with some
> means of getting the code in.

Thanks for the suggestion, but that does not fit the problem space.  The 
FPGA board I am prototyping with has an oscillator on board, just not a 
multiple of 240 kHz.  This is a very low power design and every ARM type 
CPU I have seen will consume mAs of current with the high speed crystal 
controlled clock.

One good note.  I discovered the oscillator frequency on this proto 
board is controlled by a resistor.  You can also inject a current or 
voltage to modify the frequency creating a VCO.  So I can make a first 
pass at frequency locking this oscillator.  It won't be so low current, 
but it's still better than a multi-MHz crystal.

-- 

Rick C

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Thread

Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 17:51 -0500
  Re: Low Frequency 3rd Overtone Crystal Osc Jon Elson <jmelson@wustl.edu> - 2017-03-08 17:04 -0600
    Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 19:57 -0500
    Re: Low Frequency 3rd Overtone Crystal Osc Robert Baer <robertbaer@localnet.com> - 2017-03-10 00:01 -0800
  Re: Low Frequency 3rd Overtone Crystal Osc dagmargoodboat@yahoo.com - 2017-03-08 18:02 -0800
    Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-08 18:13 -0800
      Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-09 09:11 -0500
        Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-09 08:14 -0800
          Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-09 11:24 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 11:20 -0500
      Re: Low Frequency 3rd Overtone Crystal Osc Neon John <no@never.com> - 2017-03-09 16:24 -0500
        Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-09 14:23 -0800
          Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 18:16 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc Neon John <no@never.com> - 2017-03-13 19:59 -0400
            Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-13 17:29 -0700
              Re: Low Frequency 3rd Overtone Crystal Osc bill.sloman@ieee.org - 2017-03-13 18:43 -0700
            Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 21:54 -0400
      Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-10 10:15 +0000
    Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 22:33 -0500
      Re: Low Frequency 3rd Overtone Crystal Osc o pere o <me@somewhere.net> - 2017-03-09 15:39 +0100
      Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 09:41 -0500
        Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 09:43 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 11:17 -0500
            Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 20:42 -0500
              Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 20:55 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc piglet <erichpwagner@hotmail.com> - 2017-03-11 07:37 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 03:15 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc piglet <erichpwagner@hotmail.com> - 2017-03-11 09:52 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 08:54 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 09:00 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc Jasen Betts <jasen@xnet.co.nz> - 2017-03-11 23:58 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 22:13 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-13 11:20 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-13 11:47 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-13 23:44 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-13 15:55 -0700
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 19:58 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc Jasen Betts <jasen@xnet.co.nz> - 2017-03-14 04:48 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-14 13:37 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-14 22:29 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-14 20:59 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-15 10:40 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-15 12:44 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-16 08:20 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 02:51 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-16 09:28 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 04:40 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc bill.sloman@ieee.org - 2017-03-16 05:09 -0700
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 12:47 -0400
                Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-17 00:22 +0200
                Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 19:14 -0400
    Re: Low Frequency 3rd Overtone Crystal Osc John S <Sophi.2@invalid.org> - 2017-03-13 05:51 -0500
      Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 08:39 -0400
  Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 21:09 -0500
  Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-09 20:15 -0600
    Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 23:36 -0500
      Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-10 19:02 -0600
        Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 01:15 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-11 11:04 +0200
          Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 09:31 +0000
      Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 09:15 +0000
        Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 10:50 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 16:46 +0000
        Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 15:36 -0500
          Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 23:50 +0000
            Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-11 17:59 -0600
              Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-12 08:44 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-12 20:23 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-13 12:21 +0000
                Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-14 03:30 -0500
                Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-14 20:50 +0000
  Re: Low Frequency 3rd Overtone Crystal Osc Robert Baer <robertbaer@localnet.com> - 2017-03-09 23:57 -0800
    Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-10 05:51 -0500
    Re: Low Frequency 3rd Overtone Crystal Osc Mike Jones <mikejones@gmail.com> - 2017-03-10 06:03 -0600
  Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-10 15:34 +0200
  Re: Low Frequency 3rd Overtone Crystal Osc Tim Wescott <tim@seemywebsite.really> - 2017-03-11 12:51 -0600
    Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-12 00:33 +0200
      Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-12 01:00 -0500
        Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-12 10:45 +0200
          Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-12 18:32 -0400
    Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-13 11:26 -0400

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