Page 140 - Radar Technology Encyclopedia

130 device, concentrated interaction device, MOSFET

A concentrated interaction device uses the interaction of these devices is the physical phenomenon of Vavilov-Cheren-
electron flows with concentrated electromagnetic fields. To kov radiation. In this phenomenon, with movement of the
achieve the highest effectiveness of interaction of the electron charged particles in some medium at a speed exceeding the
flow with the electromagnetic field, the latter is concentrated speed of electromagnetic waves in the given medium, these
in the smallest possible volume, and the electron flow, modu- waves are radiated. The propagation medium in the devices is
lated in density, is passed along the direction of the lines of a a slow-wave circuit. When the electron speed is close to the
force of this field. The length of the interaction space must be phase velocity of the waves in the slow-wave circuit, or
as limited as possible, and the field intensity as great as possi- somewhat exceeds it, the energy of the electrons is transferred
ble to compensate for the briefness of interaction of charge to the wave.
and field. The latter is usually achieved by using cavities with Devices of this class include traveling-wave tubes and
concentrated fields. backward-wave tubes, and, to some degree, electron-wave
Devices with concentrated interaction include resonant devices. Thanks to the extent of interaction, they have a wider
klystrons and microwave triodes. IAM bandwidth than concentrated interaction devices. IAM
Ref.: Levitskiy (1986), p. 59. Ref.: Gilmour (1986), p. 15; Levitskiy (1986), p. 83.
An electron quantum device is based on forced emission of In a fast-wave device, fast-wave interactions occur in large,
excited molecules (atoms) of an active medium. Depending smooth, multimode waveguide channels and thus involve
on the range of the operating frequencies, quantum devices higher order, overmoded resonators with large magnetic field
are subdivided into two classes. In the microwave band these requirements. Such a configuration gives much higher effi-
are masers, and in the optical band, lasers. Depending on the ciency and greater output power compared with conventional
aggregate state of the active substance, masers are usually slow-wave devices. The main representative of fast-wave
subdivided into gas and solid-state, and lasers into gas, solid- device is the gyrotron. SAL
state, liquid, and semiconductor. Depending on the operating Ref.: Currie (1987), p. 448.
mode, we distinguish between lasers operating in continuous Gunn effect device (see DIODE, Gunn).
- 3
mode, in pulse mode with a pulse duration of 10 to 10 - 6
- 7
- 9
sec, in impulse mode with a duration of 10 to 10 sec, and A gyroresonance electronic microwave device is an elec-
in the synchronization mode, at which the pulse duration can tronic device that use the interaction of a spiral electronic flux
be 10 - 10 to 10 - 12 sec. IAM with an unslowed wave in a waveguide or cavities. They are
also called cyclotron resonance masers or gyrotrons. Varieties
Ref.: Andrushko (1981), p.12; Zherebtsov (1989), p.176.
of gyrotron devices include the gyroklystron, the gyro-TWT,
An electron-wave device is a microwave device with distrib-
the gyro BWT (backward-wave tube), and the gyro-twystron.
uted interaction, in which the modulated beam of electrons
IAM
passes through a nonresisting medium in which the amplitude
Ref.: Andrushko (1981), p. 85; Gilmour (1986), p. 431.
of the space-charge waves (periodic bunches of electrons)
increases owing to the interaction of the beam with the polar- IMPATT device (see DIODE, IMPATT).
ization that it excites in the medium. The polarization waves A MESFET (metal semiconductor field-effect transistor)
have the same wavelength and phase velocity as the space- device is a field-effect transistor using a metal semiconductor
charge waves that engender them and are shifted relative to structure.
them in phase. Owing to this phase shift, they produce group-
Ref.: Currie (1987), p. 411; Golio (1991).
ing of the electron beam.
A MITATT (mixed tunneling and transit time) device is
Electron-wave devices are used to amplify microwave
the microwave device using the mixture of tunneling and
signals. The removal of energy from an electron beam can be
impact-ionization effects. It may be considered as a cross
implemented by an actively conducting medium or by a
between the IMPATT and tunnel devices. SAL
medium that has inductive conductivity. In the latter case,
plasma is used as the medium, and an electron-wave amplifier Ref.: Currie (1987), p. 403.
with such a propagation medium is classed a plasma ampli- A MODFET (modulation-doped field effect transistor)
fier. The medium with inductive conductivity may be a slow- device is a field-effect transistor using undoped GaAs mate-
wave circuit in the form of cavities in a specific frequency rial and the AlGaAs layer to form a heterojunction which
range, for which propagation of their own waves is no longer traps a two-dimensional gas between the conduction-band
possible, but the cavities themselves still possess inductive discontinuity and the bending of the conduction band due to
conductivity. charge structure. SAL
Because of the difficulty of converting electromagnetic Ref.: Currie (1987), p. 411.
waves to space-charge waves and back, electron-wave
A MOSFET (metal oxide semiconductor field effect tran-
devices have not become widely used. IAM
sistor) device is a field-effect transistor with a metal-oxide-
Ref.: Levitskiy (1986), p. 105.
semiconductor structure. SAL
An extended interaction device uses the interaction of elec- Ref.: Currie (1987), p. 478.
tron flows with traveling waves. The basis of operation of