[time-nuts] How To Measure Long Term Phase Stability Of An Oscillator

[Magnus Danielson]

Jeff,

Sorry if I was unclear in the first message, but I was tired.

The factor of 3 that I have in the first message is a huge
approximation, and could be a higher value for higher confidence
interval. It's an attempt to handle the chi-square distribution margin
for some probability of staying within. I used 3, as the traditional
engineering margin for the usual gaussian distribution, mostly because I
was to tired to dig up the propper value, but it doesn't really care as
it is an approximation never the less and in the right direction.

The underlying point is that you need to estimate the systematic and
random effects separately, and then fit them together with their quite
drastic different probability behaviors. You can't use either of the
tools as the single tool, unless you have a fairly good idea of the
dominant part, which I can't in this case.

I discussed this point with Dr. Allan, and he only knew of a pair of
articles even covering this aspect, but he agreed on the overall approach.

Cheers,
Magnus

On 09/22/2013 08:43 PM, W3KL wrote:
> Magnus.  Thanks.  Re-read your original post and along with your latest I
> now understand what's needed.
>
> I will come back if I have other questions.
>
> Thanks!
>
> Jeff
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Magnus Danielson
> Sent: Sunday, September 22, 2013 1:02 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] How To Measure Long Term Phase Stability Of An
> Oscillator
>
> Jeff,
>
> You need to measure phase with sufficient resolution and rate of time. I was
> vague on the equipment side but rater noted what you needed to do in the
> analysis-side.
>
> I would prefer to measure it at least with 10 measurements a second. Bob
> mentioned resolution, which is important as you don't want your measurement
> being swamped by measurement noise.
>
> I would use a TimePod, but not all of us have one, which is a pitty as it is
> a good instrument suitable for exactly this.
>
> Cheers,
> Magnus
>
> On 09/22/2013 02:01 PM, W3KL wrote:
>> Magnus. Thanks.  If I understand, this reduces to a measurement of 
>> frequency stability along a measurement of phase noise?
>>
>> Jeff
>>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 
>> On Behalf Of Magnus Danielson
>> Sent: Sunday, September 22, 2013 7:47 AM
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] How To Measure Long Term Phase Stability Of 
>> An Oscillator
>>
>> On 09/22/2013 01:30 PM, W3KL wrote:
>>> How does one make a measurement of the phase stability of an 
>>> oscillator over a time period much larger than the oscillator period?
>>> For example, I have an oscillator with a frequency of 4 MHz and I 
>>> want to measure the phase drift of the RF between a given point in 
>>> time and then a time 4 seconds later.  I want to make a measurement 
>>> that has a precision of 0.1 degree or better.
>> You want to measure a drift of 4/(4E6*3600) = 278 ps. You systematic 
>> frequency error can be at maximum 1.39E-10 relative, For your noise 
>> side look at TDEV at tau of 4 s, multiply that number by at least 
>> three and it should when added with peak frequency error be below 278 ps.
>>
>> Cheers,
>> Magnus
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