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In 1928 he joined the technical staff of Bell Telephone Laboratories
with the Radio Research Department, Deal, NJ where he
worked under J.C. Schelleng and E.J. Sterba. In these early days, Phil
became involved in the design and installation of
directional antenna equipment for commercial AM radio broadcasting.
In 1929 he was working in Lawrenceville, NJ, on an
antenna system which was designed to communicate by shortwave with
Europe and South America. The antenna was
connected to the transmitter by a two wire transmission line. Perhaps
the major reference at the time was J.A. Fleming's 1911
telephone equation, which expressed the impedance characteristics of
high frequency transmission lines in terms of measurable
effects of electro-magnetic waves propagating theron, i.e, the standing
wave amplitude and the wave position.
In the reprint of an article entitled "Transmission Lines for Short-wave
Radio Systems," presented at the IRE 20th anniversary
convention in April 1932, there was a footnote which read "Disclosed
to the writers by P. H. Smith, Bell Telephone
Laboratories". The footnote referred to a paragraph in the article
which began, "There is another effective way for transforming
line impedance by means of short line devices...." It was the first
published report of work done by Phil, work that ultimately led
to the creation of the Smith Chart.
In spite of his long identification and association with antenna activities,
Phil was basically a transmission-line type. He relished
the problem of matching the transmission line to the antenna, a component
which he considered matched the line to space.
Considering the frequency and the consequent large size and resultant
cumbersomeness of the antenna, the measurements were
not simple. In those early days, the sensing element was a thermocouple
bridge with about 6 or 8 thermocouples coupled to
two coils, whose dimensions were determined by the frequency of transmission.
The indicator was a microvoltmeter which
measured the magnitude of the signal. The entire assembly was then
moved along the transmission line to determine the relative
magnitude and location of the maximum and minimum signals. For transmission
lines high in the air, this required one individual
to move the sensing device along at the end of a long pole, while a
second individual would read the signal through a telescope.
It was primitive, but it worked. This was the early environment that
Phil faced as an electrical engineer with the Bell Telephone
Laboratories. For those who knew him best, it was no surprise that
he would doggedly pursue his goal of creating a chart to
simplify the work. From Fleming's equation, and in an effort to simplify
the solution of the transmission line problem, he
developed his first graphical solution in the form of a rectangular
plot.
Phil persisted in his work, the diagram gradually evolved through a
series of steps. The first rectangular chart was limited by the
range of data it could accommodate. He was aware of the limitations
and kept working on the problem until some time in 1936,
when he developed a new diagram that eliminated most of the difficulties.
The new chart was a special polar coordinate form in
which all values of impedance components could be accommodated. The
data for this diagram was scaled from the earlier
rectangular diagram. The impedance coordinates in this case were not
orthogonal and were not true circles, but, in the form
chosen, the standing wave ratio was linear. The chart closely resembled
what ultimately became the final result.
Phil, however, suspected that a grid made up of a system of orthogonal
circles might be more practical. He felt it would have
distinct advantages, particularly as regards reproducibility. With
this in mind, he spoke to two of his co-workers, E.B. Ferrell
and J.W. McRae. Because they were familiar with the principles of conformal
mapping, they were able to develop the
transformation whereby all data from zero to infinity could be accommodated.
Fortunately, curves of constant standing wave
ratio, constant attenuation and constant reflection coefficient were
all circles coaxial with the center of the diagram. The scales
for these values, while not linear, were entirely satisfactory. A diagram
designed along these lines was constructed in early
1937. It was essentially the form still being used today.
Smith approached a number of technical magazines with regard to publication
of the Chart, but acceptance was slow. There
were not many technical magazines at the time, and none in the microwave
area. However, in January of 1939, after a delay of
two years, the article was printed in Electronics magazine.
A fact one cannot ignore is that many highly competent people proposed
charts for use in solving transmission line problems.
Some of their charts had brief periods of popularity, but it is a comment
on Phil's persistence in searching out the ultimate
solution, that his Chart stands out above all others in its use and
usefulness.
It took a while for Phil to convince other people of the utility of
his chart. One of the first individuals to see its value was A.G.
Fox at Bell Labs, who in 1939 found it useful in some early work he
was doing on the new subject of waveguides. When the
M.I.T. Radiation Laboratory was formed in 1940, the value of the Smith
Chart was recognized immediately and it was put into
general use. According to Phil, the M.I.T. workers were his first customers.
It would be hard to visualize many of the
achievements of the M.I.T. Rad Lab without some help from the Smith
Chart. For microwave people at that period, the Smith
Chart had the equivalent impact of turning on a bright light in a previously
dark room.
Phil published a second article in 1944 which incorporated further improvements
including the use of the chart with either
impedance or admittance coordinates. In 1958, in the first issue of
the Microwave Journal, a biography of Phil was published to
acknowledge the importance of his contribution. In a series of 6 subsequent
issues of the magazine, Dr. George Southworth
described the importance and some of the applications of the Smith
Chart.
According to Dr. Southworth, the Smith Chart, even in its earliest form,
was no sudden flash of genius. Phil's first ideas were
imperfect and they required time for full maturity. However, as Dr.
Southworth wrote, "it was to his everlasting credit that he
did not allow his idea to die on the vine, but nourished it until he
had brought it to a high degree of perfection".
Today's emergence of the digital computer as a dominant design tool
has in no way diminished the importance of the Smith
Chart. The Smith Chart has become the ultimate background for both
computer and measurement instrument displays.
Phillip Smith Beyond the Smith Chart
Had he not invented the Smith Chart, Phil would still deserve to be
honored for his many contributions to technology. Just
before America's entry in World War II, he was sent with a small group
of engineers to Fort Hancock to work with the Signal
Corps Laboratories on a most important secret weapon - radar. He spent
a year on Sandy Hook designing antennas and
related components for production of the SCR-268 radar. Later, he worked
on early microwave radar antenna developments
for submarine use under W.H. Doherty at Whippany, NJ. In his early
professional career, while developing 500 kw coaxial line
components for radio station WHAS in Louisville, Kentucky, he obtained
a basic patent on the optimum conductor diameter
radio for a coaxial transmission line. This is the outer to inner diameter
ratio of a coaxial line which results in maximum power
handling capability for a given outer conductor diameter. Smith said
this was one of the simplest patents ever granted - the only
claim was the single number 1.65. Another basic patent he obtained
was for the adjustable matching stub tuner.
After World War II he worked on the design of FM broadcasting antennas
for Western Electric broadcasting equipment.
During that period he invented the famous "Cloverleaf" antenna. Later
he became involved in military weapon radar systems
studies and designed and supervised groups responsible for the electrical
design of the DEW LINE, NIKE ZEUS and the
ABM System, which became SAFEGUARD.
One of the programs he worked on that can help to illustrate his creativity
in microwave technology was an acquisition radar
system on the Island of Kwajalein, in the South Pacific. This was an
experimental system in the early days of the
SAFEGUARD program. The design of the antenna involved using a Luneburg
lens technique. The classical Luneburg lens is a
spherical lens that has the property that when the lens intercepts
a plane wave, the focal point of the wave will always appear at
a point perpendicular to the wave itself on a line through the center
of the sphere at a point on the opposite surface of the
sphere, regardless of the direction from which the plane wave approaches
the lens.
This made it possible that when a signal was received, by virtue of
the location of the receivers and the action of the Luneburg
lens, one could determine the azimuth and elevation of the target.
The technique that was used at Kwajalein was to build one half of the
sphere - that is a hemispherical Luneburg lens - with a
ground plane significantly larger than the diameter of the sphere itself.
The lens was made up of a series of polyfoam cubes
about 2' x 2' x 2' loaded with aluminum slivers, so that the polyfoam
block had a uniform dielectric constant throughout. By
varying the amount of aluminum slivers, one could vary the dielectric
constant of the block. The required values of dielectric
constant were then determined to achieve the Luneburg lens performance.
It turned out for their system they needed about 10
to 12 different values of dielectric constant and perhaps dozens of
each value. The system worked as predicted by theory.
The operation of the antenna relied on the ability to build the homogeneous
aluminum-loaded polyfoam blocks of different, but
precise dielectric properties. The idea for the blocks came from Phil.
This episode helps to highlight one of Phil personality
traits. As a friend of his commented, "he could be oh so stubborn."
And "on occasion that stubbornness had a profound effect."
Against the wisdom of some of the most distinguished consultants at
Bell Labs, Phil maintained that by the random distribution
of the aluminum slivers the dielectric constant could be controlled
both as to homogeneity and value so as to serve the needs of
the project. The test proved he was right.
Personal Notes
Phil married Rosine Rittenhouse around 1930. They had three children.
Donald was born in 1932 and is currently a Pastor.
Stephen, born in 1936, is an engineer and founded Basic Research Corporation
in 1993. A daughter, Sharon was born just
after the war.
Stephen recalls that around 1945 Phil used surplus components to assemble
a television on top of a card table in their home.
NBC was broadcasting 1 to 2 hours a night on channel 4 out of New York.
As town folk regularly gathered to view the new
marvel, Phil enclosed the entire table top to prevent contact with
the HIV circuitry. Phil also had an interest in building boats,
usually small boats with outboard motors.
In 1950 Phil took up private flying, eventually purchasing his own plane.
He loved to fly and accumulated over 1500 flight hours
in the U.S., Bahamas, Cuba, Mexico and Canada. On one eventful trip
to Lexington, Phil, with son Stephen and Wally Smith
(an unrelated coworker), ran afoul of a weather front and was forced
to make an ungraceful landing in New London,
Connecticut. Wally apparently refused to fly with Phil again.
Phil was continuously active in the IRE and later the IEEE from 1947
on. Phil served on and chaired numerous IEEE
committees, including technical standards Committee 2 on Antennas and
Waveguides. In 1952 he was elected IEEE Fellow
"for his contributions to the development of antennas and graphical
analysis of transmission line characteristics". He was
secretary-treasurer of the Antennas and Propagation Society in 1954.
He is a past member of Commission 6 of URSI, and a
member of the Delta Chapter of Tau Beta Pi.
In March of 1958, he and his bride, Anita Macpherson from Maplewood,
N.J., flew in their private plane to Cuba for a
honeymoon. On September 21, 1964, their daughter was born. Penny Smith
Robbins is an electrical engineer with Bellcore in
Chester, NJ.
Toward the end of his career he continued to work as an individual contributor.
Although he had the perks of a supervisor, he
chose not to be a manager. His function was to look at anything and
everything and contribute. And he did, in the very best
sense of the word. He was completely happy in his environment.
He was a hands on engineer and was not particularly mathematical. When
he had a problem to solve and recognized that he
needed some special help, he would not hesitate to seek it out. He
was highly organized and super meticulous. When he was
sure he was right, there was no way to make him back down.
The first edition of this book Electronic Applications of the Smith
Chart in Waveguide, Circuit, and Component Analysis,
was published by McGraw-Hill in 1969. He also authored an article on
the Smith Chart for The Encyclopedia of Electronics
published by Reinhold Publishing Company in 1962 and 35 papers on antennas
and transmission lines. Phil has 20 U.S. patents
in the microwave field including the basic patent on the transmission
line matching stub, the Cloverleaf antenna, and the optimum
power ratio coaxial transmission line. Phil retired from Bell Labs
in 1970.
At its annual symposium in 1975 the MTT presented him with a Special
Recognition Microwave Application Award for his
invention and application of the Smith Chart.
The Smith Chart was eventually manufactured and sold by at least two
companies. When Phil retired from Bell Labs he
organized Analog Instruments Company of New Providence, NJ - which
initially merchandised simple navigational instruments
for light aircraft, but later began supplying his charts and a dozen
or more chart-related items. Through 1975 Analog
Instruments has sold about 9 million copies to engineers and educators
all over the world. The Smith Chart is currently selling at
the rate of about a ton per year. The company is still operated by
his wife Anita.
Phil Smith passed away on August 29, 1987.
In 1989, the 50th anniversary of the Smith Chart was celebrated at the
MTT International Microwave Symposium in Dallas,
Texas. Much of the material in this biography was taken directly from
material prepared for that celebration.
In 1994, Phil was elected to the New Jersey Inventors Hall of Fame.
Acknowledgements
I would like to thank Phil's wife Anita for providing much of the material
used in this biography. Portions were taken directly
from material prepared by Theodore Saad, Robert Mattingly, George Dale,
and the Microwave Journal. Other details were
provided by Stephen Smith
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