[time-nuts] Conditioning clock signal paths

Stephan Sandenbergh stephan at rrsg.ee.uct.ac.za
Wed Jun 28 14:02:11 EDT 2006

-----Original Message-----
From: Magnus Danielson [mailto:cfmd at bredband.net] 
Sent: 28 June 2006 07:02 PM
To: time-nuts at febo.com; stephan at rrsg.ee.uct.ac.za
Subject: Re: [time-nuts] Conditioning clock signal paths

From: <stephan at rrsg.ee.uct.ac.za>
Subject: Re: [time-nuts] Conditioning clock signal paths
Date: Wed, 28 Jun 2006 18:35:09 +0200
Message-ID: <006401c69ad0$d2356eb0$401c9e89 at Stephan>

>> Hi Magnus,

>Hi Stephan,

>> So I guess the verdict is that it is best to band limit your clock signal
>> with a low-pass filter. This filter is then still supposed to still allow
>> the necessary rise time for adequate PSSR.

>That would only solve your problem partly, and also, as you pull your
>down in frequency you could actually worsen your situation as you lower the
>slewrate as you cut away the overtones which contribute to a quick

>No, what you have to do instead is to increase the slewrate gain. You
>want an amplifier to have sufficient linear gain around your trigger point
>that the output of the amplifier is basically slew-rate limited. Any
>noise will also be amplified, but as the slope is amplified the time-
>they cover at the trigger point is much smaller and hence the noise-induced
>trigger-jitter is reduced. Naturally, if you in the process add alot of
>you can spoil your result.

Hi Magnus,

Thank you for the excellent advice. From what I understood is this: the
higher your slew rate the smaller the time epoch onto which you map the sum
of your signal and the noise. This decreases the jitter in a proportional
relationship to you slew rate. Am I missing the point completely? How does
this relate to bandwidth limiting to reduce noise? (to me it seems it only
applies to sinusoids then?). 

Best regards,


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