[time-nuts] Fwd: 10MHz to 80MHz frequency multiplier suggestions
SAIDJACK at aol.com
SAIDJACK at aol.com
Wed Feb 2 20:12:38 UTC 2011
Hello Raj,
our ULN-1100 and ULN-2550 GPSDO's use a 100MHz VCXO locked to the 10MHz
OCXO via an ADF4002 PLL with less than 40Hz bandwidth. After careful
optimization of the layout and the loop filter, the phase noise results are quite
excellent at 100MHz, see the attached plot. The plot shows two versions of
the PLL loop filter from the design phase of the products, one has been more
optimized. You can see that the noise floor is almost -170dBc/Hz at 100MHz.
You get the best of two worlds: the absolute frequency accuracy of the
GPSDO, and the very low phase noise of the VCXO above the PLL bandwidth. It is
clearly visible that the VCXO phase noise inside the loop bandwidth is
actually also reduced by locking it to the 10MHz OCXO (the PN curve below the
loop bandwidth frequency of ~30Hz would just continue going up without the
PLL)
Low Noise 100MHz VCXO's are readily available at mouser and digikey (so
are 80MHz units), and programming the ADF4002 is straight forward with the
help from the AD online tools. It can be bit-banged with any microcontroller.
bye,
Said
From: Raj <_vu2zap at gmail.com_ (mailto:vu2zap at gmail.com) >
Date: January 31, 2011 21:11:46 HST
To: Discussion of precise time and frequency measurement
<_time-nuts at febo.com_ (mailto:time-nuts at febo.com) >
Subject: Re: [time-nuts] 10MHz to 80MHz frequency multiplier suggestions
Reply-To: Discussion of precise time and frequency measurement
<_time-nuts at febo.com_ (mailto:time-nuts at febo.com) >
I was contemplating the same thing. I fed the output to a bifilar
transformer and
diode doubler and got good results. I have to add an amp and double it
again twice
more. It is still on breadboard. The object was to multiply the error 8x
and compare.
Probably a PLL locking to 80 Mhz will retain the long term accuracy of the
TBolt reference.
Raj, vu2zap
At 31-01-2011, you wrote:
I'd like to convert the 10MHz output of a Thunderbolt to 80MHz: it should
be
used as a 3.3V clock for an A/D converter.
Even if I have already taken a look to documentation from KO4BB and Wenzel
regarding frequency multiplier,
I'm asking if you have some more references or even better, some schematics
of a working 8x multiplier.
. thanks in advance
_ Elio Corbolante.
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