This full-page advertisement by
Bell Telephone Laboratories in the June 1956 issue of Radio & television News
seems to imply that their Dr. S. Weisbaum and/or his contemporaries was/were
the original developer/s of the waveguide isolator. If so, it would be no surprise
since Bell Labs was responsible for many technology innovations during its history
- RF, microwaves, telephony, information theory, switching, transmission lines,
test and measurement, and much more. Other information available on the Internet
assigns credit to
Bell Labs in the same timeframe. From the ad:
"This isolator is a slab of ferrite which is mounted inside the waveguide, and is
kept magnetized by a permanent magnet strapped to the outside. The magnetized ferrite
pushes aside outgoing waves, while unwanted reflected waves are drawn into the ferrite
and dissipated. Bell physicists discovered this action during their fundamental
studies of ferrites."
Bell Telephone Laboratories Isolators
Radio's One Way Street
Dr. S. Weisbaum assembles an isolator which he developed for use in a new microwave
system. Dr. Weisbaum is a Ph.D. in microwave spectroscopy from New York University.
He is one of many young men at Bell Laboratories applying the insight of the physicist
to develop new systems of communication .
New radio relay systems for telephony and television now in the making will employ
an ingenious device invented by Bell scientists. The device, known as an "isolator,"
senses which way microwaves are traveling through a waveguide, and stops those going
the wrong way.
In the new systems a klystron wave generator sends signals through a waveguide
to the antenna. The klystron must be shielded from waves reflected back along the
waveguide by the antenna. The isolator stops reflections, yet allows the transmitted
signals to go through clear and strong.
This isolator is a slab of ferrite which is mounted inside the waveguide, and
is kept magnetized by a permanent magnet strapped to the outside. The magnetized
ferrite pushes aside outgoing waves, while unwanted reflected waves are drawn into
the ferrite and dissipated. This "field displacement" action results from the interplay
between microwaves and a ferrite's spinning electrons. Bell physicists discovered
this action during their fundamental studies of ferrites.
This is another example of how Bell Telephone Laboratories research works to
improve American telephony and telecommunications throughout the world.
The heart of the isolator is a ferrite slab. Geometric pattern is a carbon layer
which dissipates reflected signals.
At a radio relay station an isolator assures one-way transmission from the output
of the amplifier to the antenna.
Bell Telephone Laboratories
World Center of Communications Research and Development
Posted June 3, 2019