[time-nuts] GPS: ADEV or MDEV?

Magnus Danielson cfmd at bredband.net
Sat Apr 21 23:32:34 EDT 2007


From: "Christopher Hoover" <ch at murgatroid.com>
Subject: Re: [time-nuts] GPS: ADEV or MDEV?
Date: Sat, 21 Apr 2007 20:06:59 -0700
Message-ID: <001c01c7848b$4adfa5c0$c401000a at fakie>

> 
> Bruce wrote:
> > 6) Doesn't rely on the relative phase of an independent oscillator being
> > random with respect to the PPS signal or the OCXO signal. This is rarely
> > satisfactory unless one makes heroic efforts to isolate the oscillator
> > from the PPS and the OCXO. Injection locking of the "independent"
> > oscillator is almost inevitable unless there is sufficient isolation.
> 
> I am surely exposing my ignorance here, I don't completely understand this.
> 
> The independent oscillator is being used to measure the TI of the PPS, is
> that correct?
> 
> If so, let's presume this oscillator is clocking a free running counter, the
> value of which is being captured on the edge of the PPS and sent to a
> processor (for sawtooth correction, filtering, etc.). 
> 
> How does injection locking occur?

The PPS signal triggers the trigger and pulls the supplies and this inject
into the oscillator. If you think according to similar lines there is more in
the signal integrity line.

Cheers,
Magnus



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