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EARLY TRANSISTOR
AND DIODE HISTORY AT BELL LABS Art Uhlir Jr. |
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Oral History – Art Uhlir Jr. (Continued) |
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Please provide additional
comments regarding varactor diode development at Bell Labs. Varactor harmonic generators were shown to give enough
transmitter power for applications unreachable with existing transistors
alone, with ominous portent for Bell hegemony in long-distance communication.
Receiver protectors using varactors and PIN diodes were developed for
military radars. Diode microwave switches had been made with computer diodes,
but the diffused-silicon PIN diodes permitted optimizing the compromise
between switching speed and power handling. Already by 1951 (in time to be presented at the 1951 Princeton
Inn course) W. T. Read (of dislocation fame) had already analyzed the
proposition of using avalanche multiplication to produce substantial
microwave power (5 watts at 6 Ghz).
Seven years later we had silicon “dimple diodes” made for high power
harmonic generation and I thought to put one in a waveguide and bias it into
avalanche. Sure enough, microwave power came out. Read’s theory was published in the same year. [REF 6]. Having a sense that Research might be
feeling that I was front-running them a bit too much with quick experiments,
I called this observation to their attention. What resulted was a
professional quantitative study of the phenomenon as it existed, and a
journal article. [REF 4]. |
I wanted to get a spectrum analyzer and put in tuners to get a
narrow spectrum and more power.. But
all spectrum analyzers were tied up in systems development; new ones were
more expensive in 1958 dollars than modern ones are in 2004 dollars. John Moll left for Stanford and Hewlett
Packard and I left for Microwave Associates. So it was left to Barney DeLoach
of our old department to get significant power out of fairly ordinary
diffused silicon computer diodes, a decade later. [REF 5]. Better heat sinks
lead to production IMPATT diodes, but they did not seem to have much appeal
in the conventional continuous-wave communications systems which were
functioning well with the precise frequencies available from varactor
harmonic generators. After your pioneering work
with microwave diodes at Bell Labs, you left and joined Microwave Associates.
What was your position there? At Microwave Associates I came in as Director of Semiconductor
Research in 1958 and worked to proselytize the use of junction diodes in
microwave devices. The company's total sales of T-R tubes, waveguide
circuits, magnetrons, and point-contact diodes was then about $3 million.
They were making more money on point-contact silicon diodes than the total
for the company. Their MA 1N23E diodes mixer diodes were envied by Western
Electric. Go
To Uhlir Oral History, Page 10 |
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