[time-nuts] Re: Interfacing a 8dBm sine output of an OCXO to a digital logic standard

Alberto di Bene dibene at usa.net
Fri Sep 16 10:00:08 EDT 2005

>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
In my own GPSDO I have used this circuit : 
It was taken from the book "Experimental methods in RF design" and works 
quite well, though no specific measurements of phase noise degradation 
have been made.
The 10 MHz input is coming from an Isotemp OCXO, which delivers abt 3.5V 
pk_to_pk open circuit

73  Alberto  I2PHD

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