[time-nuts] filtering a 10Mhz frequency standard?

gary lists at lazygranch.com
Tue Dec 13 16:27:54 EST 2011


If you are going to buffer the output, why does the filter have to be 
passive? Did I miss something here? Today 10MHz is in the realm of 
active filters. [Hey, not that I made an active filter at 10MHz.]

Sensitivity is a function of the denominator. The only advantage to a 
LPF over a BPF is the BPF has to be centered at 10MHz, while you could 
bump the corner of the LPF to a higher frequency so there is less 
sensitivity at 10MHz This presumes you are only getting rid of harmonics 
and not spurs.

For lowest component sensitivity, leap frog designs are best. But in 
continuous time designs, they require many op amps per pole.




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