[time-nuts] Help w/integration problem
John Ackermann N8UR
jra at febo.com
Mon Jan 2 09:09:21 EST 2006
Hi Mike --
I can't speak for John, but I'd sure find that program useful.
73,
John
----
Mike Feher said the following on 01/02/2006 08:10 AM:
> John -
>
> I wrote a program about 20 years ago to calculate the total integrated noise
> power from the individual power spectrum density points. It is in GW Basic
> and I still use it almost daily. Let me know if you would like it. 73 - Mike
>
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of John Miles
> Sent: Monday, January 02, 2006 3:00 AM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Help w/integration problem
>
> Does anyone have a piece of C (BASIC, whatever) code that turns an array of
> dBc/Hz values into integrated RMS noise?
>
> I'm trying to use a simple rectangular integrator to divide a log-log plot
> into "bins":
>
> for (i=L_column; i < U_column-1; i++)
> {
> sum += ((value[i] - ((value[i] - value[i+1]) / 2.0)) *
> (frequency[i+1] - frequency[i]));
> }
>
> This just takes the midpoint dBc/Hz value between successive columns of a
> phase-noise plot, multiplies it by the frequency step between the columns in
> question, and sums the result for all columns in the range of interest.
>
> The output of this process, when I feed a typical noise graph with values
> around -110 dBc/Hz to it, with frequency values at the lower and upper
> limits of 1000 and 10000 Hz, is around -1E+6. What I'd *like* is a value
> corresponding to the "-63 dBc" value cited on pages 7 and 8 in this Zarlink
> app note:
>
> http://assets.zarlink.com/CA/Phase_Noise_and_Jitter_Article.pdf
>
> In this note, the author shows a noise curve similar to the ones I'm working
> with, and magically pulls -63 dBc out of the ether with no explanation of
> the integration process that obtained it. (What does it mean, in the
> author's words, to take the area "under" a phase-noise curve, anyway?
> What's the bottom dBc/Hz value?)
>
> Being from the instant-gratification generation, I really don't want (and
> won't understand) a calculus lecture. I want the 5 lines of code that do
> the integration. :-) This is for the next release of my freeware GPIB
> noise-measurement app, so your karma will be integrated along with the noise
> if you're able to help!
>
> -- john, KE5FX
>
>
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