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Extracting the 5th Harmonic
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March 13th 04, 04:51 PM
Paul Burridge
Posts: n/a
On 13 Mar 2004 07:33:15 -0800,
(Tim Shoppa)
wrote:
Fifth harmonic frequency multipliers do exist, but it's usually much
easier to double and triple your way to the final frequency if possible.
(You just discovered this, I think!)
Yeah, but trying to get the 5th is hardly asking for the moon...
The lack of even harmonics is typical of push-pull stages ... if you
are messing around with CMOS gates, you might try using a TTL gate
(which pulls low much stronger than it pulls high) or an open collector
TTL gate, both with smmallish (100-200 ohm) pull-up resistors for
doubling.
I've a reasonably fast Schmitt I'm going to stick in there in place of
the 74HC04 before I resort to anything fancy (same pin-out).
Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz?
Because I don't have a rock lying about for that fundamental!
Hopefully some supreme being here will spot a problem with the traces
I've now posted...
--
The BBC: Licensed at public expense to spread lies.
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