OOK modulation naming

A friend recently showed me an OOK modulation that I had never seen
before, and I’m wondering if anyone knows a name for this scheme.

It is PWM where both the on periods and off periods carry data in their

In the example we observed, an on or off period with a duration of two
units represents a zero. An on or off period with a duration of one
unit represents a one. Example:


This sequence of amplitudes represents the binary data 011101001.

Note that this scheme has a variable data rate. (Two packets carrying
the same number of bits may have different durations.) Overall,
however, the data rate is higher than in a similar looking scheme in
which data are encoded only in the on periods.

Does anyone know what to call this? I am tempted to call it Biphase



Why not make the ratio 1:3 and then you could call it Morse PWM. :slight_smile:

Hey Mike,

I think that NRZI.

  • Jeff

I though NRZI had a constant symbol rate. I would expect 011101001 in
NRZI to look like:



Great find, Jeff! I’m also finding it called “Digital Pulse Interval
and Width Modulation” with the same acronym. I think it is clearer with
the “and” in there, and that version of the name dates back at least to


After way to much searching … under Anisochronous modulation, there is
something called Digital Pulse Interval Width Modulation (DPIWM).

Seems like as good a name as any.

  • Jeff