[time-nuts] Modulation Domain Analysis

Bill Byrom time at radio.sent.com
Tue Jun 16 22:18:53 EDT 2015

On a related subject: Tektronix TVC501 Time-Interval to Voltage Converter (cousin of the modulation domain analyzer)

I have worked as an Application Engineer at Tektronix for over 25 years.
In the early 1990's we developed the TVC501, which was a time interval
to voltage converter. I'm doing this from memory (since it's hard to
find references on the Internet) but I believe it had a time interval
counter with about 50 ns resolution. The counter output was subtracted
from a user-settable reference time, then multiplied by a user-settable
gain before driving an 8-bit D/A. The analog voltage output was updated
at each measured interval, up to about 2 million updates/sec. This
architecture allowed the user to see small changes in large time
intervals on either an analog or digital oscilloscope or other
instrument. So you could see changes in the period of the power line
frequency with around 100 ns resolution, and use the oscilloscope
voltage level trigger features to capture timing aberrations. The TVC501
was a single-wide TM500 plug-in unit.

The TVC501 had two BNC inputs, and could sense the width or period of
signals on one input, or the time interval between edges on the two
inputs. It was a rather specialized product, and I don't think we sold
many of them. In 1995 we discontinued nearly the entire TM500/TM5000
line. Some of these products were sold by Tegam for a few years.

Bill Byrom N5BB
On Tue, Jun 16, 2015, at 05:17 PM, Richard (Rick) Karlquist wrote:
> That's interesting.  I worked for the HP Santa Clara Division
> from 1979 until just before it was closed in 1998.  I
> forget who "invented" MDA at SCD, but it was hyped like
> it was some new concept and I never heard anything about
> the HP9540.
> Many times someone would come to me and ask me about
> some "new" bright idea they had, and I would tell them
> "Yes, I can confirm that your idea is excellent, because
> I read the original paper on it that was published in
> 19XX."  It is interesting that people would often get
> mad at me, as if it is my fault they reinvented the wheel.
> If only I known about your HP Journal article, I could
> have throw it up to the "innovators" at SCD.
> Before I worked for HP, an HP Journal article came out
> about fractional-N synthesizers, and everyone at Zeta
> Labs was anxious to use the technology in the Zeta
> Labs designs.  Except one guy, who pointed out that
> he had invented frac-N 11 years previously, and he
> called it "digiphase."  I've never heard anyone at
> HP ever acknowledge that guy.
> Rick (now retired from HP/Agilent/Keysight)
> On 6/16/2015 12:54 PM, Robert Gilchrist Huenemann wrote:
>> I stumbled onto the time nuts list from a posting on modulation domain analysis a couple of weeks ago. I am enjoying the discussion.
>> I want to comment on modulation domain analysis, or phase digitizing. This is a technique that uses a period mode frequency counter, or two such counters back to back, to recover the modulation history of a frequency modulated waveform.
>> This technique was first used in the HP9540 automated transceiver test system. This system was described in the August 1973 HP Journal. The HP9540 used a single HP5326 period mode counter with a 10 MHz clock. At that time, no counter was available with a higher clock frequency.
>> A breadboard system was assembled as part of the HP9540 development effort which used two HP5326 counters back to back. To insure that alternate periods were measured, the second HP5326 ran off the gate output of the first. However, it was realized that the characteristics of the HP9540 and its specific application were such that two counters were not required. Please refer to my HP Journal article for details.
>> The HP9540 was developed at HP's Automatic Measurement Division. This division was disbanded in 1974.
>> Modulation Domain Analysis and Phase Digitizing were terms that came into use with the later development of specialized stand alone instruments that combined computational capability, back to back period mode counters, higher clock frequencies, interpolation and algorithms for various measurements. All of these were worthwhile improvements on the basic technique first used in the HP9540.
>> I would be happy to answer questions. Thank you for allowing me to post this information.
>> Robert Gilchrist Huenemann, M.S.E.E.
>> 120 Harbern Way
>> Hollister, CA 95023-9708
>> 831-635-0786
>> bobgh at razzolink.com
>> https://sites.google.com/site/bobhuenemann/
>> Extra Class Amateur Radio License W6RFW
>> IEEE Life Member 01189471
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