Page 242 - Radar Technology Encyclopedia
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JOINT, microwave klystron, antiklystron 232
JOINT, microwave. Microwave joints are connections of K
two transmission lines of the same type, providing reliable
electrical contact. The joints must ensure retention of match-
The KABANOV EFFECT is the phenomenon wherein HF
ing and power-handling capability of the circuit with mini-
radio waves, after reflection from the ionosphere, are dis-
mum induced damping of power and without parasitic
persed after they have reached Earth's surface. Some part of
radiation.
the dispersed radiation is returned by the reverse path to the
In high-frequency joints (connectors) of coaxial cables,
source of the radiation where it can be detected. The reverse-
the contacts are provided using spring clamps and plugs held
dispersed signals can be picked up at ranges from several
in the connection by external threaded or other connections.
hundreds to thousands of kilometers. Over-the-horizon
The sections of the waveguides are connected using
(OTH) radar operation is based on the Kabanov effect. IAM
flanges of two types: contact and choke. The contact flanges
Ref.: Druzhinin (1967), p. 114.
require careful working and strict parallelness of the touching
surfaces. In the choke flange the contact is made through a KLYSTRON. The klystron is a velocity-modulated micro-
serial short-circuited loop (see CHOKE, microwave). wave linear-beam tube using one or a series of cavities and a
For connecting transmission lines that rotate relative to slow-wave structure to achieve power generation and amplifi-
one another, rotary and rolling joints are used. IAM cation. It was invented in 1939 and was initially relegated to
Ref.: Sazonov (1988), p. 53. the role of a local oscillator in superheterodyne receivers.
The klystron has proven to be quite important for radar
A rolling joint is an element of a transmission line intended
applications. The main advantages of this device are high
for turning one part of a circuit relative to another without
average and peak power (tens of megawatts of peak power
disturbance of the electrical contact and the quality of match-
are available); high gain (26 to 60 dB is conventional, and
ing. If the turning angle is great, then the design of the rolling
even 90 dB was reported); high efficiency (35 to 75%); low
joint is analogous to that of the rotary joint. When the turning
interpulse noise; and good compatibility with sophisticated
angle is small, a set of several sections of rectangular
pulse-compression waveforms. The main disadvantages are
waveguides is used. They automatically assume intermediate
relatively low bandwidth, compared with traveling-wave
angular positions relative to the input and output sections of
tubes (10 to 12% for multicavity klystrons); relatively high
the joint. The smooth transition formed here does not cause a
operating voltages; and large physical size.
change in the standing-wave ratio at the point of twist of the
Klystrons are manufactured for wavelengths from 70 to
waveguides. IAM
80 cm to several millimeters and are used primarily as high-
Ref.: Perevezentsev (1981), p. 214.
power oscillators and amplifiers in radar transmitters, and for
A rotary joint is an element of a transmission line intended low-power local oscillators in receivers (typically in the cen-
for rotating of one part of a circuit relative to another without timeter wave bands).
disturbance of the electrical contact and the quality of match- Some types of high-power klystrons are listed in
ing. A wave with axial symmetry is excited in rotating adapt- Table K1. IAM
ers, so either round waveguides or coaxial lines are used in Ref.: Lavrov (1974), p. 348; Andrushko (1981), pp. 18, 23; Gilmour (1986),
such joints. Rotating and fixed parts of a line are connected hap. 9; Ewell (1981), pp. 54–64.
using choke-flange (for waveguide lines) and coaxial choke
The antiklystron is an electronic vacuum microwave device
connections (see CHOKE, microwave), which provide the
that uses centrifugal electrostatic focusing of the electron
electrical contact between moving surfaces. IAM
beam. One feature of the antiklystron is the use of a system
Ref.: Sazonov (1988), p. 55; Pereverzentsev (1981), p. 213.
with multiple interaction of the rotating stream of electrons in
JOSEPHSON EFFECT. The Josephson effect is the tunnel- the HF field (the beam passes several times through one and
ing of linked pairs of electrons through an insulating barrier the same region of interaction with the field). Thanks to the
between two superconductors. The accumulation of current in multiple handling of the electronic beam, “accumulation of
the presence of critical bias voltage has an extremely pro- modulation” occurs in the system. In the antiklystron, the pre-
nounced nature, which determines the pronounced inflection ceding turns are directly connected to subsequent ones
of the volt-ampere characteristic. The Josephson effect is through the beam itself, and there is a feedback circuit of the
used in millimeter signal mixers. The Josephson mixer is dis- subsequent turns with the preceding ones through the HF
tinguished by a low level of shot noise (see NOISE, shot) and field. The feedback circuit is possible when the grouped elec-
low power of the control oscillator (less than 1 mW). IAM trons enter the braking phase of the HF field. Here there will
Ref.: Tucker, J. R., Appl. Phys. Lett. 36, no. 6, 1980. be an increase in the energy of the HF signal due to the energy
of the electron beam.
The antiklystron can operate as an oscillator with the
ability to tune over a broad band. IAM
Ref. Popov (1980), p. 39.