[time-nuts] LTE-Lite module

SAIDJACK at aol.com SAIDJACK at aol.com
Fri Oct 17 14:32:49 EDT 2014

Hello Jim, 
let me answer through Time Nuts as this may interest  other parties as 
Yes, using a fast flip flop to generate 10MHz out of  the 20MHz TCXO 3.0V 
CMOS output from the LTE-Lite module will preserve the phase  noise (actually 
improve it by up to 6dB due to the 20log(n/m) noise improvement)  and will 
not add any spurs if you use the clean 3.0V output from the LTE-Lite  module 
or an external clean power supply (please note the LTE-Lite TCXO RF  output 
is 3.0V due to the internal 3.3V to 3.0V Low Noise regulator feeding the  
TCXO and buffer). 
Use fast logic such as 74AC74, 74FCT74, or the like.  We do exactly that on 
our ULN-2550 boards to generate 50MHz and 25MHz out of the  100MHz, and 
using a fast CMOS divider will result in additive phase noise  that will be 
below the crystal oscillator phase noise floor. 
That will result in significantly better phase noise and  much lower spurs 
than using the synthesized 10MHz output from the board, and one  74' chip 
can generate both 10MHz and 5MHz out of the 20MHz LTE-Lite output. This  is 
exactly what we would do here if we needed a clean 10MHz from the 20MHz  
LTE-Lite board. 
I believe you can order low-noise divide-by-2  blue-top boxes from Wenzel 
already packaged-up and connectorized as  well. 
Hope that helps,
Hi Said 
I was one of those looking for 10Mhz but I just thought  again now that it 
might be just as well to divide the standard 20Mhz output by 2  using a FF. 
I think that would preserve all the desirable characteristics of the  20Mhz 
signal which I understand to just be square wave at CMOS 3.3v levels  
anyway. Is that correct? 

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