GB605198A - Improvements in or relating to attenuating apparatus for high-frequency electromagnetic energy - Google Patents

Abstract

605,198. Attenuators. SPERRY GYROSCOPE CO., Inc. Aug. 1; 1945, No. 19836. Convention date, Aug. 2, 1944. [Class 40 (viii)] An attenuator which may also be an impedance-transformer is adapted for insertion in a coaxial cable or a wave-guide and comprises an impedance-transformer composed of a section of transmission line filled with solid dielectric, attenuation being produced by dissipation of energy in the dielectric and/or in lumped shunt conductances. The diameters of the conductors may be the same as or different from those of the transmission lines with which the device is in circuit. In one embodiment, Fig. 1, energy is dissipated in a poorly conducting shunt disc 9, which is supported by a mass 8 of solid dielectric, such as polystyrene, a quarter of a wavelength long and having a dielectric constant of such a value that the impedance seen from the left of the attenuator is matched to the line. If, however, the admittance of the dissipator 9 has a reactive component or susceptance, the length of the section 8 is changed so that a purely conductive admittance is seen from the left of the attenuator, the requisite length being formed from a circle diagram, Fig. 3 (not shown). A symmetrical attenuating section 8<11>, Fig. 4, having two dissipators 9<11>, may be associated with junctions comprising outer sleeves 21 and quarter-wave inner conductors 19, the length of the dielectric 8<11> being chosen from a circle diagram, Fig. 5 (not shown), to match the resistance and neutralize susceptance at the left of the attenuator. The coaxial lines connected to the attenuator may have different characteristic admittances resulting from the use of inner conductors with different diameters, Fig. 4. Symmetrical impedance-matching may be effected by the use of three dissipators 9<11> spaced apart in the dielectric 8<11>, Fig. 6 (not shown), at distances determined from a circle diagram, Fig. 7 (not shown). Alternatively, the discs 9<11> may be omitted and dissipative material, such as carbon particles, may be incorporated in a half-wave section of dielectric 8<11>, Fig. 8 (not shown). The characteristic impedance of the attenuator may be changed by changing the diameters of its conductors, Figs. 9 ... 12 (not shown), and may, by a suitable choice of dielectric and diameter-ratio, be made equal to that of the empty line, dissipative discs 25<1>, 261, 27<1>; Fig. 10, being incorporated so that the electrical effect is equivalent to that of attenuators described in Specification 617,236. The attenuator may be of the wave-guide instead of the coaxial type, Figs. 13, 14 (not shown).