Am 22.01.2016 um 22:40 schrieb jimlux:
the oscillator is a HCMOS output, so figure swinging about 3.5V
Output.. I'm feeding differential clock inputs on ADCs. I'll bet a
+/- 300mV swing would work.
4)Title said "Low Noise" needs better definition as to what kind of
noise and how far down. Are we to be concerned about harmonic and spur
content as compared to real random white noise?
This is time-nuts.. it has to be perfect..
But realistically, my source is probably going to be about -90dBc/Hz
at 1 Hz, -125 at 10Hz, -145 at 100 Hz. I'm going up by a factor of
10, so I'd expect 20 dB worse plus a little..(nothing is perfect, eh?)
Call it maybe -100 to -95 at 10 Hz, -125 to -120 at 100 Hz and so forth.
harmonics are interesting: it's the sample clock into an ADC. So
harmonics of the 100 aren't a big deal. harmonics of the 10 or 20
are. If you have significant 90 or 110 contaminating the 100, then
you get weird spurs.. (I had this problem on a software radio where
the 50 MHz sample clock was contaminated with some 66 MHz from the CPU)
Spurs cause the same issues.
ON the other hand... spurs that are pretty low don't make much
difference if you're digitizing a signal that is close to the noise
floor: the spur multiplied by the desired signal is usually lower and
down in the noise. Strong CW in band signals, though, are a real pain.
<
https://picasaweb.google.com/103357048842463945642/Tronix#6079270188048833778
>
I think that top left board would not be far away:
in : 10 MHz LVDS or CMOS
in: 3V3
out: 100 MHz CMOS 3V3
just a few hours wall clock time from layout to working as a
ham radio weekender, so please excuse my diy home board
production process.
Ok, the use of a 4046 descendant may not be the last word
from a timenut perspective, but I'll redo it with an osc of
my own anyway. Divider 100/10 is a LVC163 (161?) + lvc04.
< http://www.crystek.com/crystal/spec-sheets/vcxo/CVHD-950.pdf >
Digi-Key has 153 of them on a tape and 441 of a similar one , even
cheaper that seems to point to the same data sheet.
<
http://www.digikey.de/product-detail/de/CVHD-950-100.000/744-1213-ND/1644128
>
You can get the few dB missing close-in by transfer from your reference.
In the picture:
The bottom row of boards is a doubler 100->200 MHz using 2*BF862, slight
gain,
and diode doubler 200 -> 400 MHz, SAW filter to get rid of
100/200/300/500/600 +/-10 etc,
post amp to get a usable level again.
Still missing 400-> 800, 800->1600 to feed _my_ ADC clock input.
regards, Gerhard
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