Stephan Sandenbergh wrote:
I wondered if anyone could help me with an interfacing problem? I guess
that it is a trivial question to those that know, but I am rather
puzzled by it.
My very stable OCXO output a 8dBm (50ohm) sine wave. How is this signal
converted/interfaced to a logic standard (e.g. LVDS)? I can imagine that
the sine wave must be squared off using a fast comparator and then fed
through to a logic driver. Are there any integrated IC's out there that
does this? It would be rather sad to sustain substantial phase noise
degradation due to a floating comparator threshold and limited slew
rate.
Stephan, I don't know if this is the *best* answer, but I've stolen an
idea used by Brooks Shera in his GPSDO controller. He uses the input
section (only) of a 74HCT4046 PLL chip to square the OCXO signal. I
implemented his idea using a 74AC4046 and it seems to work OK, though I
don't know what its jitter/phase noise performance is. A schematic of
my circuit is at http://www.febo.com/time-freq/gps/z3801a/mods/index.html.
John
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