Barkhausen-Kurz tube
Encyclopedia
The Barkhausen-Kurz tube, also called the B-K oscillator, was commonly used in early electronic systems
operating in the ultra-high frequency (UHF) portion of the radio spectrum
.
of the triode
vacuum tube, it was realized that the upper frequency for use by this device was limited by the spacing between internal components. Even with the smallest of spacing, the frequency limit for early triodes was in the low megahertz. A technique called velocity modulation was theorized to overcome this limitation.
In 1920, Heinrich Barkhausen
and Karl Kurz at the Technische Hochschule
in Dresden, Germany used the velocity modulation theory in developing the retarded-field triode that could provide UHF operation. Although severely limited in output power, the Barkhausen-Kurz tube was quickly adopted world-wide for UHF research. This device is also called the retarded-field and positive-grid oscillator.
This oscillatory motion of the electron cloud continues, with some electrons lost to the grid at each passage and constituting the output signal. The lost electrons are replenished by new emissions by the cathode. The time for one complete cycle is the period of the generated signal. This time, and thus the output frequency, could be somewhat varied by changing the relative potentials.
Subsequent to the development of the Barkhausen-Kurz device, a number of other similar devices for UHF applications were invented. All of these are classified as "reflex oscillators," the best known being the klystron
.,
Electronic Systems
Electronic systems are groupings of electronic circuits and components which are designed to accomplish one or more complex functions. Examples include telecommunication systems, computer systems, power distribution systems, radar systems, electronic music systems, and many others.Electronic...
operating in the ultra-high frequency (UHF) portion of the radio spectrum
Radio spectrum
Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz ....
.
Development
After the development by Lee de ForestLee De Forest
Lee De Forest was an American inventor with over 180 patents to his credit. De Forest invented the Audion, a vacuum tube that takes relatively weak electrical signals and amplifies them. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use...
of the triode
Triode
A triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electronic amplification device...
vacuum tube, it was realized that the upper frequency for use by this device was limited by the spacing between internal components. Even with the smallest of spacing, the frequency limit for early triodes was in the low megahertz. A technique called velocity modulation was theorized to overcome this limitation.
In 1920, Heinrich Barkhausen
Heinrich Barkhausen
Heinrich Georg Barkhausen , born at Bremen, was a German physicist.Born into a patrician family in Bremen, he showed interest in natural sciences from an early age...
and Karl Kurz at the Technische Hochschule
Technische Hochschule
Technische Hochschule is what an Institute of Technology used to be called in German-speaking countries, as well as in the Netherlands, before most of them changed their name to Technische Universität or Technische Universiteit in the 1970s and in the...
in Dresden, Germany used the velocity modulation theory in developing the retarded-field triode that could provide UHF operation. Although severely limited in output power, the Barkhausen-Kurz tube was quickly adopted world-wide for UHF research. This device is also called the retarded-field and positive-grid oscillator.
Operating principle
The Barkhausen-Kurz triode operates with the grid (a thin mesh of wires) at a positive potential relative to both the cathodes (or filament) and the anode (or plate). The negative electrons emitted from the cathode are accelerated toward the positive grid, but easily pass through the grid’s wide spacing. Past the grid, the negative anode repulses the electrons, stopping their velocity just before reaching the anode surface. They are then accelerated back toward the grid, again pass through the wide spacing, and are then repelled by the negative cathode, stopping just before reaching the surface. Bunching occurs when the velocity becomes zero, resulting in a moving cloud of electrons.This oscillatory motion of the electron cloud continues, with some electrons lost to the grid at each passage and constituting the output signal. The lost electrons are replenished by new emissions by the cathode. The time for one complete cycle is the period of the generated signal. This time, and thus the output frequency, could be somewhat varied by changing the relative potentials.
Subsequent to the development of the Barkhausen-Kurz device, a number of other similar devices for UHF applications were invented. All of these are classified as "reflex oscillators," the best known being the klystron
Klystron
A klystron is a specialized linear-beam vacuum tube . Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern...
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External links
- http://authors.library.caltech.edu/6970/1/POTpr32b.pdf Potapenko, G., "Investigations in the field of ultra-short electromagnetic waves," Phys Rev, Vol. 39, Feb. 13, 1932, pp. 625–638