T
Tom Bruhns
Try this approach-- a high-bit counter circuit to measure period. Pop
the period output of the counter into a simple DAC, and scale it however
you need to. Use this as one input to an analog multiplier, and the other
input would be your phase. Turn that voltage into a delay somehow-- a
simple 555 timer charging via some constant current, for example (I haven't
checked speed specs on a 555). The constant current charging means a ramp
to the control voltage.
No ucontroller, no DDS, one counter, a DAC, a multiplier, and a 555 with a
transistor.
(Need a register between the counter and the DAC...)
Let's see--instead of a counter to get the period and a DAC to turn
that into an analog voltage--why not just a ramp that's reset by the
square wave, and a peak detector to monitor how big the ramp gets?
The peak detector output is proportional to the waveform's period.
It's kind of the analog of a frequency-to-voltage converter, but it's
a period-to-voltage converter. You don't really even need a peak
detector; a simple average (e.g., long time constant RC filter) will
do fine, since the frequency doesn't change in use and I can in this
case depend on the stability of the duty cycle of the input.
But how I turn the 555's output to a delay (on a 120MHz square
wave...), I'm a bit foggy on...
On the other hand, I know how to use a voltage to control a wideband
delay pretty well...so this has some possibilities. Thanks for the
idea!
Cheers,
Tom