[sdiy] frequency doubling

[Mountain Man]

Hi folks,

Thanks very much for all the input on my Xpander powersupply; I'll be
doing some testing over the weekend based on these comments :)

On a different topic, I'm interested in building a frequency doubling
circuit.  There was some talk here a while back which I haven't been
able to find in the archives.  The gist, as I recall, was to create a
50% duty cycle square with the same frequency as the original circuit,
then use leading and falling edges to create trigger pulses.  I
understand most of this, but there are two parts of the process I'm
unclear on.  First, how would I create a 50% square wave from a
non-symetric input (if its symmetric about a known voltage, I know to
simply use a comparator).  In particular, I have a square wave that's
not 50% - what do I need to do to it.  The other part is how to convert
narrow trigger pulses (after doubling) back into something like a square
wave or triangle.  I know how to get fixed-width pulses (using a 555 for
example), but that won't work well over a range of frequencies.
Suggestions?

Thanks as always,
Elby