Best copy (plus correction)
Two electric currents in
two directions down the same piece of wire. http://www.ivorcatt.co.uk/x87tned.htm
; 1 ; 2
Fast Pages 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , some of which is in two
of my books. The argument starts at page 30 of one book , and at page 4 of the other book
, continuing on page
5 . Here in
figure 9.2 we see “a very narrow pulse introduced at the front end of the
active line. If there were no parallel passive line nearby, this pulse
would travel down the active line (at the speed of light for the
dielectric) more or less unchanged,” in a TEM mode. “However, as the other
two traces show, the presence of the passive line caused the original
narrow pulse to break up into two similar pulses.”
The error in this paper . Simplified Exposition of the error
Developments from this paper
42 years later. January and September 2011
Crosstalk (Noise) in Digital Systems
Ivor Catt, IEEE Trans. Com. Vol. EC-16
No. 6, dec1967, pp743-63.
viens d’ajouter deux et deux at je suis arrive a quatre.
vois que peut-etre il y a un peu du Francais atour de vous; votre nom, et votre pays.
number of factors come together. You have French connections. You said you
were involved in Electricity Board power lines.
will take you through the way I came upon the idea of two velocities of
In Motorola Phoenix Arizona in 1964 I
investigated the problem of interconnecting high speed (1 nsec) logic gates. To avoid interconnection delays, the
system had to be reduced in size, leading to a 13 layer printed circuit
mother board. Alternate layers had signal lines and voltage planes.
I decided that one key problem was to determine
the amount of crosstalk between two parallel lines, either surface or
buried. First, I found a flat topped pulse getting onto the other line,
which disproved the idea that dv/dt or di/dt created the noise. However, there was a further
puzzle; a big spike at the end of the flat topped noise pulse.
My mentor Ken C Johnson, whom I had left when I
moved from Ferranti in Manchester England, happened to run in to me in the
corridor of Motorola Phoenix. I grabbed him, and he told me there were two
modes involved. He then shot back to England. However, he got them wrong.
If the active and passive lines are A and P, and their mirrors (below the
voltage plane, which acts as a mirror) are B and Q, he said the modes were,
firstly, between A and P on the one side to B and Q on the other; and the
other mode was between A and B on the one side, and P and Q on the other.
This second mode he gave incorrectly. However, he gave me the important
clue, to look for two modes. (See pp32, 33, figs. 39 and 40 in my 1995 book
which you bought from me, for the correct two modes.)
In due course I worked out the correct two
modes, A and P to B and Q (Even Mode) and A and Q
to B and P (Odd Mode). I proved my theory with high speed pulses and
photography, see my 1967 paper.
Before Ken turned up, I read Jarvis, who had
brewed up the correct equations. However, then, to “simplify” the problem,
he removed certain “minor” terms. This was a disaster, because it
unbalanced the equations and prevented him from getting the correct result.
In fact, his resulting formula was ridiculous, with noise increasing more
and more until it could be larger than the incident signal. I said either
he was wrong, or we had an amplifier!
I worked out my own equations, and solved them,
see p30 of my 1995 book, now at www.ivorcatt.com/em.htm
Jarvis referenced Cotte,
and after I had worked it all out (as I remember) I got two articles by the
Frenchman Cotte, dated 1947 and 1954. He had the
equations, but upside down, and he did not resolve them as I did (see p30
of my 1995 book). I am writing all this from memory, because the Cotte papers are somewhere in the roof here. I am
certain he did not “solve” the equations, and that he could not do so
because, as with Jarvis, they were upside down.
Some time later I discovered that in Microwave,
the two modes were known (but not the two velocities – IC, 2014). However, working in digital electronics,
knowledge in the Microwave camp was not available to me. I reference Oliver
as my 4th reference at the end of my 1967 paper. I reference Cotte, who wrote in French, at my 5th and 17th
references. (I spoke French at that time, and do so now.)
As I remember, Cotte worked
on overhead power lines.
I wrote this because (1) you have a French name
and are in Canada; (2) Cotte, who wrote in
French, was involved in the problem of crosstalk early on; (3) my memory
says that, like you, he was involved in overhead power lines.
It is likely that you are not concerned with
crosstalk, but merely with transients (switch on/off of lightening) in
overhead power lines. However, since Cotte got
into crosstalk, and (as I remember) worked on overhead power lines, then
crosstalk in that situation may be of importance.