[time-nuts] Square to sine wave symmetrical conversion (part 2)

[Magnus Danielson]

Hi,

On 07/25/2015 03:35 AM, Charles Steinmetz wrote:
> skipp  wrote:
>
>> [the 10MHz output is] not even close to being symmetrical.  The waveform
>> on-portion (duty cycle) appears (surprising to me) to be much less
>> than 20%
>>
>> Now I'm under the assumption that proper rounding or conversion of the
>> non
>> symmetrical 10 MHz square to a sine wave will be a bit more involved.
>
> That means there are significant even harmonics present, including the
> second harmonic, which is a lot closer to the fundamental and,
> therefore, harder to remove by filtering (a perfect square wave contains
> only the fundamental and its odd harmonics).

If the symmetry error is minor, the second harmonic at 20 MHz will still 
be relatively small. However, it if turns out to be important, an 
LCR-serial link tuned to 20 MHz and with some resistance for 
sufficiently low Q can eat some of that energy up as it is placed 
between signal and ground.

Cheers,
Magnus