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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.
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