Microwave Tubes

During the 1930s, the Bell Telephone Laboratories began investigating the use of shortwave electromagnetic radiation for long-distance communications. The high bandwidths that could be achieved, as well as the potential for line-of-sight transmissions over many miles, was promising. The U.S. Army and Navy were also interested in shortwave electromagnetic waves as navigational aids and for aircraft detection systems. But progress was hampered by the lack of electron tubes able to function at the necessary frequencies of a gigahertz or more.

Then in 1937, working at Stanford University with his brother Sigurd, Russell Varian invented the klystron; the first successful microwave tube, it could oscillate and amplify signals at frequencies as high as 3 GHz, corresponding to a wavelength of 10 centimetres. Klystrons modulate a stream of electrons traveling along the tube axis into bunches that generate microwave radiation at an output resonator gap. Like all microwave tubes, their high-frequency operation does not depend on small device dimensions.

A bit later Henry Boot and John Randall invented the cavity magnetron at Birmingham University. These British physicists employed a resonant cavity structure in a magnetron for the first time. It was a huge success, generating kilowatts of microwave power at 10 cm - far more than klystrons could then achieve. Soon after U.S. physicists and engineers learned about this surprising electron device in 1940, the MIT Radiation Laboratory was established to develop comprehensive radar systems with the cavity magnetron as the core element. Small klystrons served as local oscillators in these systems, which eventually operated above 10 GHz by the end of World War II. Radar proved crucial to the Allied victory.

Originally trained as an architect, Austrian emigrant Rudolf Kompfner invented another kind of microwave tube, the traveling-wave tube, at Birmingham in 1943. After he learned about this invention during the War, Bell Labs engineer John Pierce developed a working theory of its operation, based on the interaction between an electron beam and slower electromagnetic waves traveling within the tube. His theory contributed to the tube's stability and the realization of its broadband capabilities. Pierce developed other new features that vastly improved these tubes - such as a convergent electron gun now named after him. Kompfner came to Bell Labs in the early 1950s and worked with Pierce to adapt traveling-wave tubes for satellite communications, which began in the 1960s with the Echo and Telstar satellites. Traveling-wave tubes are the only electron devices able to supply the proper combination of high output power and bandwidth needed for satellite communications.

Today, modern traveling-wave tubes are still used extensively in microwave and satellite communications systems because of their high efficiency, long lifetimes and excellent reliability. And modern klystrons can produce astonishing levels of peak and average power - more than 100 MW peak and 1 MW average. They power particle accelerators used for physics research and cancer therapy, and are employed in high-resolution radar systems. Magnetrons are also widely-used today because they are efficient, low-cost sources of microwave power. Every commercial microwave oven contains a magnetron.

Exercise 5

Continue the following questions to the text.

1. When did Bell Labs …?

2. What were the U.S. Army and Navy …?

3. Why was the progress …?

4. What did the brothers Varian …?

5. How do klystrons …?

6. Where was cavity magnetron …?

7. How did the U.S. physicists …?

8. Did small klystrons …?

9. When was the traveling-wave tube …?

10. What was Pierce’s theory …?

11. What improvements …?

12. What electron devices are able to …?

13. Why are modern traveling-wave tubes …?

14. Where are klystrons and magnetrons …?

LESSON 9

Exercise 1

Translate the following words paying attention to word-building affixes.

Microwave, waveform, wavelength, waveguide, waveband, wavefront, waveshaping, microphone, superheterodyne, superconductivity, semicircle, semiconductors, semiaxis, semioscilation, hemisphere, conjecture, conjectural, conjectured, trap, trapping, trapped, formation, forming, formed, deform, uniform, non-uniform, uniformity, uniformly, unidirectional, universal, uninteresting, advantage, disadvantage, advantageous, line, linear, linearity, nonlinear, convert, convertible, reconvert, conversion, cooperate, coordinate, coexist, closely, close, disclose, displace, dissimilar, disregard, out, output, outside, outsider, outward.

Exercise 2

Translate the following paying attention to noun groups.

1.Bluetooth was developed initially by Ericsson as a short-range (10meters) cable replacement for linking portable consumer electronic products, but it also can be adapted for printers, fax machines, keyboards, toys, games, and virtually any other digital consumer application. 2. More than 2000 organisations have joined the Bluetooth Special Interest Group (SIG) and most of them are currently developing Bluetooth-enabled products. 3. A Bluetooth radio consists of a radio-frequency (RF) transceiver portion, baseband link control unit, and the associated link management software, plus an antenna subsystem. 4. The radio uses Frequency-hopping spread-spectrum technology to support both point-to-point and point-to-multipoint connections. 5. The Bluetooth baseband protocol allows for both circuit- and-packet switching, making it suitable for both voice and data. 6. Hoping to speed the Bluetooth products to market the SIG has formed the Bluetooth Measurement Initiative, whose task is to work with test equipment manufacturers to develop hardware and software for interoperability testing. 7. In October Tektronix began shipping the CMU 200 universal radio communication tester announced in June. 8. With several companies, mostly start-ups like San Diego’s Silicon Wave and Britain’s Cambridge Silicon Radio it is going to be difficult to face the reality of creating electronics products with an entirely new communication interface. 9. The new standard specifies a set of wavelengths for use in what is known as coarse wavelength-division multiplexing (CWDM) system.10. When powered only by its on-board nickel-metal hybrid batteries, the robot can walk for about twenty minutes at most. 11. Its browser-like interface, which is independent of the underlying network topology, is integrated with a speech synthesis system. 12.Much of the research into optical interconnects in the U.S. have been funded by a US $ 70 million program run by the U.S. Defence Advanced Research Projects Agency. 13.Since 1992, drive storage capacity has been increasing at an annual rate of 60 percent, and over 100 percent in recent years – a rate exceeding the 18-month doubling of Moore’s law for IC complexity. 14.Wireless network engineers will have to add bandwidth management to the frequency planning and the code and noise management skills. 15. The spin-on and chemical deposition processes differ basically in how they deposit a thin low- k dielectric film on a silicon wafer. 16. The Coral and Black Diamond dielectrics are made by adding carbon to silicon dioxide recipe in a chemical vapor deposition (CVD) process that yields carbon-doped oxide.

Exercise 3

Match the antonyms.

1. common 2. to receive 3. to increase 4. to trap 5. before 6. failure 7. advantage 8. to push 9. easy 10. far 11. inside 12. together 13. next 14. different 15. to begin

1. disadvantage 2. to finish 3. outside 4. special 5. previous 6. same 7. success 8. separately 9. difficult 10. to decrease 11. to liberate 12. after 13. to pull 14. close 15. to send

Exercise 4

Match Ukrainian translations to the following English phrases.

1. solid-state	1. транзистор з точковим контактом
2. “field-effect” amplifier	2. сумiжнi шари
3. point-contact transistor	3. легований домiшками
4. junction transistor	4. дiйсно величезний
5. adjacent layers	5. твердотiльний
6. “doped” with impurities	6. пiдсилювач на польовому транзисторі
7. hearing aids	7. площинний транзистор
8. truly immense	8. слуховi апарати

Exercise 5

Pay attention to translation of the following phrases.

1. it proved a failure -	виявився невдалим;
2. stumbled upon a way to overcome -	спотикалися на шляху до переборення;
3. it took several major advances -	це потребувало кiлькох значних успiхiв;
4. had begun to have a major impact -	почала дуже впливати;
5. push back the scientific frontiers even further - ще ширше розсунути межi науки.

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