[time-nuts] RE: Micro phase stepper

Tom Clark w3iwi at toad.net
Mon Jul 18 17:14:36 EDT 2005

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

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


   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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