GB585066A - Wave-signal transmission lines - Google Patents

Abstract

585,066. High-frequency transmission lines. HAZELTINE CORPORATION. Oct. 26, 1944, No. 20912. Convention date, Jan. 28. [Class 40 (iii)] A folded high-frequency transmission line, whose length may be adjustable, is so dimensioned that coupling between successive folds of its inner conductor is reduced and the line is in consequence electrically long though physically compact. The inner conductor may comprise a loop 14, 15, Fig. 1, forming the inner conductor of a section of coaxial line, the screen 19 forming a common outer conductor for both legs 14, 15 of the loop. Since these legs are not screened from one another, they are subject to mutual coupling which shortens the line electrically, but this effect is reduced by making the width D of the screen, Fig. 2 (cross-section at 2-2, Fig. 1) substantially less than the distance between the legs 14, 15, so that the electric images formed in the screen tend to neutralize the effect of each leg on the other. The nearest distance between the surfaces of the legs must be at least equal to, and preferably twice as great as, the width D, and the side walls of the screen are parallel to the median plane of the loop 14, 15. The external connections are effected through two jacks 24, 24 of the coaxial type. The loop 14, 15 is telescopic and its length is adjusted by means of a rod 21, and in order that the characteristic impedance may be invariable, a movable end wall 16 is mounted integrally with the loop 14, 15 and is connected to the screen 19 through contact fingers 20 or capacitively. Alternatively, the transmission line may comprise a pair of parallel loops enclosed in an outer screen whose sides are parallel to the medium planes of the loops, Fig. 3 (not shown), and in this case each loop is screened by the other loop and one side of the outer screen. The line may be electrically lengthened by providing a solid dielectric between the extensible part of the loop 14, 15 and the screen 19, Figs. 4 ... 8 (not shown), and in order that the characteristic impedance may not thereby be reduced, the distributed inductance is increased by making the extensible part of the loop of flat strip and by suspending finely divided magnetic material in the solid or liquid dielectric. The screen 19 may have an elliptical cross-section.