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Old 13th October 2012, 11:29 PM   #701
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
First, injection locking lends itself better to a SVO since you have two low pass filters to exploit to reduce any contributions from the locking signal. There is a lot on serious analysis on injection locking and associated jitter/phase noise in the lit. Usually the close in phase noise is from the external source (XO in my case) and the noise further from the carrier comes from the locked oscillator. So a good low distortion oscillator locked by a good crystal based oscillator should be even better.

Second, even with a PLL you need a frequency control element that is voltage controlled. The Boonton does this with an external CPU controlled PLL and tuning via voltage on an analog multiplier in the cosine section I think. It works quite well actually with the output frequency very precisely locked.

Locking Victor's oscillator can be done with a small signal into the bottom of the AGC (for example). The larger the pull needed the larger a signal is needed with the distortion going up as well. Pulling under 1% should be pretty benign however.

This is very interesting. Can you direct me to some lit on this?
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Old 14th October 2012, 02:09 AM   #702
1audio is online now 1audio  United States
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You can find a lot of difficult stuff and old stuff with a Google search of "injection locked oscillator". I figured it out from lots of reading snippets here and there. The Time Nuts e-mail history has a lot that may help.

I can scan and post the Boonton Oscillator circuits if that helps.
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Old 14th October 2012, 05:18 AM   #703
davada is offline davada  Canada
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Originally Posted by 1audio View Post
You can find a lot of difficult stuff and old stuff with a Google search of "injection locked oscillator". I figured it out from lots of reading snippets here and there. The Time Nuts e-mail history has a lot that may help.

I can scan and post the Boonton Oscillator circuits if that helps.
Hi Demian,

Just reading the wiki on it is enough.

Thanks
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Old 14th October 2012, 02:03 PM   #704
KSTR is offline KSTR  Germany
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Demain & David,

thanks for the info, I'll have a look at it.

-----:-----

Returning to basic fixed freq super-oscillators, anybody have experience with the design of the 10kHz osc from LT (LT app note 67, page 62ff)? The clever composite opamp building blocks based on high speed CFB opamps used there look promising as does the ALC control element based on a transconductance amp, haven't seen that elsewhere.

A unity-gain stable composite with 120dB gain at 10kHz is something not seen every day, maybe it is of use for notch filters, lowpasses and IMD signal mixers etc, too. And for real applications like preamps etc...

For sure construction and adjustment/verification of this osc is an extremely daunting task. How is one supposed to check residual distortion of a claimed "parts-per-billion"-grade osc?....
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Old 14th October 2012, 04:52 PM   #705
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Quote:
Originally Posted by 1audio View Post
You can find a lot of difficult stuff and old stuff with a Google search of "injection locked oscillator". I figured it out from lots of reading snippets here and there. The Time Nuts e-mail history has a lot that may help.

I can scan and post the Boonton Oscillator circuits if that helps.
I've never been a big fan of injection locking, always preferring a PLL where possible. If you need to lock your oscillator to your VCO, you can adapt some of the auto-tune circuitry in my THD analyzer to make a PLL that locks the SVF oscillator.

Cheers,
Bob
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Old 14th October 2012, 05:28 PM   #706
davada is offline davada  Canada
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Originally Posted by Bob Cordell View Post
I've never been a big fan of injection locking, always preferring a PLL where possible. If you need to lock your oscillator to your VCO, you can adapt some of the auto-tune circuitry in my THD analyzer to make a PLL that locks the SVF oscillator.

Cheers,
Bob
Hi Bob,

I was thinking of your auto tune circuits when I wrote about this.
How much ripple would you say comes from those circuits and does it get in the way?
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Old 14th October 2012, 05:48 PM   #707
1audio is online now 1audio  United States
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Quote:
Originally Posted by Bob Cordell View Post
I've never been a big fan of injection locking, always preferring a PLL where possible. If you need to lock your oscillator to your VCO, you can adapt some of the auto-tune circuitry in my THD analyzer to make a PLL that locks the SVF oscillator.

Cheers,
Bob
Is there a reason? PLL's tend to be complicated and an injection locking scheme is pretty simple, essentially dropping out of the circuit when not in use. What is the benefit of the PLL? If you are using like the Boonton for precise tuning across a broad range I can see it but for a fixed oscillator it may be overkill.
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Old 14th October 2012, 06:18 PM   #708
1audio is online now 1audio  United States
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Quote:
Originally Posted by KSTR View Post
Returning to basic fixed freq super-oscillators, anybody have experience with the design of the 10kHz osc from LT (LT app note 67, page 62ff)? The clever composite opamp building blocks based on high speed CFB opamps used there look promising as does the ALC control element based on a transconductance amp, haven't seen that elsewhere.

A unity-gain stable composite with 120dB gain at 10kHz is something not seen every day, maybe it is of use for notch filters, lowpasses and IMD signal mixers etc, too. And for real applications like preamps etc...

For sure construction and adjustment/verification of this osc is an extremely daunting task. How is one supposed to check residual distortion of a claimed "parts-per-billion"-grade osc?....
I thought someone had built this and posted info on it. Some of the LT app stuff has proven really hard for me to duplicate and this was so off the wall I did not try. I would like to see the layout they used to make it work.

Ultra low distortion audio oszillator the never ending search for a pure sine is one effort with unbelievable breadboarding. If someone has a layout that worked I would be interested.
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Old 14th October 2012, 06:30 PM   #709
davada is offline davada  Canada
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Quote:
Originally Posted by KSTR View Post
Demain & David,

thanks for the info, I'll have a look at it.

-----:-----

Returning to basic fixed freq super-oscillators, anybody have experience with the design of the 10kHz osc from LT (LT app note 67, page 62ff)? The clever composite opamp building blocks based on high speed CFB opamps used there look promising as does the ALC control element based on a transconductance amp, haven't seen that elsewhere.

A unity-gain stable composite with 120dB gain at 10kHz is something not seen every day, maybe it is of use for notch filters, lowpasses and IMD signal mixers etc, too. And for real applications like preamps etc...

For sure construction and adjustment/verification of this osc is an extremely daunting task. How is one supposed to check residual distortion of a claimed "parts-per-billion"-grade osc?....
I think it's more like this.

"Super Gain Block Oscillator Circuitry
When A1, as described above is connected with U1, as
shown in Figure 89, the resulting circuit is not only unitygain
stable but has open-loop gain of 180dB at 10kHz".

There is at least one thread on the forum and if you google you will find a bit more.
It will require careful layout and ground planes.

I think the 1ppb was more a theoretical number. I haven't heard of anyone actually measuring this. What analyzer goes down this low?
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Old 14th October 2012, 06:56 PM   #710
davada is offline davada  Canada
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Quote:
Originally Posted by KSTR View Post
Demain & David,

thanks for the info, I'll have a look at it.

-----:-----

Returning to basic fixed freq super-oscillators, anybody have experience with the design of the 10kHz osc from LT (LT app note 67, page 62ff)? The clever composite opamp building blocks based on high speed CFB opamps used there look promising as does the ALC control element based on a transconductance amp, haven't seen that elsewhere.

A unity-gain stable composite with 120dB gain at 10kHz is something not seen every day, maybe it is of use for notch filters, lowpasses and IMD signal mixers etc, too. And for real applications like preamps etc...

For sure construction and adjustment/verification of this osc is an extremely daunting task. How is one supposed to check residual distortion of a claimed "parts-per-billion"-grade osc?....
Check this out here.

DIY Test Equipment for Audio and Ham Radio Enthusiasts
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