clock divider schems ...

[Don Tillman]

   Date: Wed, 15 Apr 1998 01:34:44 -0700
   From: Kevin Lightner <majmoog at synthfool.com>

   What I've tried only as an experiment and would be neat to develop further
   (anyone? :) would be to cascade these doubler stages (possibly with a one
   shot or flip flop in between stages).

   Any thoughts on cascaded freq doublers?

(nI'm probably a little confused on the context here, but that never
stopped me before...)

The best frequency doubler scheme I know of is, given a square wave
input, run it through a simple single-pole low-pass filter tuned so as
to be an integrator with some leakage, fully overdrive that (ie,
compare it to zero), and XOR that with the original signal.  

Basically XOR-ing two square waves 90-degrees apart will give you a
double-frequency 50% duty cycle square wave.  Surely it gets pretty
weird as the frequency changes in a real world application.  But
hey... 

This circuit has appeared a few times in EDN and Electronic Design
magazines.

  -- Don