Ulrich, DF6JB asked
can someone please explain to me how a micro phase stepper works?
Is it
a pure digital device or does it make use of analog delay line
techniques? What is the maximum delay and what is the delay step
size?
Here I describe two different types of phase steppers:
1. If you are trying to precisely delay a pulse train, take a look at
Maxim's programmable delay lines at
[1]http://www.maxim-ic.com/products/timers/delay_lines.cfm. The
DS1020 series is available with 8 bits of binary programmable
steps with resolutions of 0.15, 0.25, 0.5 1 or 2 nsec per step and
total delays in the 50-500 nsec range (see
[2]http://www.maxim-ic.com/appnotes.cfm/appnote_number/107 ). This
will work to delay an arbitrary pulse train If you look on
[3]GPSTIME for my "Timing for VLBI 2005" version and scroll down
to slides 21 and then 25-27, you'll see why commercial GPS
receivers have a "sawtooth" jitter on their 1PPS outputs, and how
it is being removed in a commercial product.
2. If you want to phase delay a sine wave, a simple trick is to use a
double-balanced mixer to up-convert from a VFO. Pass the signal
thru a long coax delay line. Then use the SAME vfo to down-convert
back to the original frequency with another mixer. As you tune the
VFO, you change the phase delay at the output.
Hope that helped -- 73 de Tom, W3IWI
References
1. http://www.maxim-ic.com/products/timers/delay_lines.cfm
2. http://www.maxim-ic.com/appnotes.cfm/appnote_number/107
3. http://gpstime.com/
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