[time-nuts] 10MHz Square to Sine Wave Conversion

[Charles Steinmetz]

Skipp wrote:

>The GPSDO I recently acquired outputs a 10 MHz square wave. I'd like
>to convert it to a sine wave and I am looking for suggestions

A simple Tee network works well (see below).  The input resistor can 
be chosen from 50 to around 200 ohms to suit the particular output 
circuit used in your unit.  As the value is reduced, the sine wave 
output will increase (until you hit the current limit of the GPSDO 
output stage).  Use the lowest value that still gives good distortion 
performance.  If the sinewave output amplitude is too large, increase 
the input resistor.

If the sinewave output amplitude is too small, you can either add a 
linear amplifier after the filter, or run the square wave from the 
GPSDO into several high-current CMOS gates in parallel and then 
through the Tee network (in that case, you would use one input 
resistor from each of the output gates rather than tie the gate 
outputs directly to each other).

Best regards,

Charles

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