GB753989A - Improvements relating to high-frequency apparatus - Google Patents

Abstract

753,989. Transmission line terminations. BIRD ELECTRONIC CORPORATION. Feb. 4, 1954 [Feb. 4, 1953], No. 3365/54. Class 40 (8). An absorptive termination for a coaxial line comprises a resistive inner conductor 40 and a tapered outer conductor 42, the inner conductor being surrounded by a conduit 118 along which a liquid dielectric coolant flows. The termination is enclosed within a liquidtight container 1 having a removable top 10 to which the termination is attached. The cylindrical top portion 44 of the logarithmically tapered outer conductor 42 fits within an annular locating member 45 which is a sliding fit within the container 1. Rigidly secured to the top of the annular member 45 is a perforated tubular member 50 which extends through a central opening in the top 10. The inner conductor 40 is in the form of a ceramic tube coated externally with a film of carbon. Its upper end fits within a socket in the lower end of a cylindrical conductive connector element 64 which is coaxial with the tube 50 and is formed with a frustoconical portion 69. This portion forms, together with the annular member 45, a transition section between the termination and a coaxial line which is connected to the terminals 50, 73. The inner terminal 73 is provided with a socket 74 for a connecting plug and has a shank of reduced diameter which fits within the central bore of a cylindrical block 60 of polytetrafluoroethvlene. In order that the shank 75 may be held firmly within the block 60 it is formed with slots 87 whereby it can be expanded by a screw-driven expander (Fig. 8, not shown) to interlock with the block. Set screws 56 ensure that the block is firmly located within the tube 50. The lower end of the outer conductor 42 is provided with a cylindrical section 95 spaced from the inner conductor 40 and a further cylindrical section 97, Fig. 11, of reduced diameter which is forced into contact with a brass terminal band 100 on the inner conductor by split rings 99. The brass terminal band is secured to the inner conductor by layers of copper and solder deposited upon the carbon film. In order to compensate for the fact that the end sections 95, 97 of the outer conductor are now-logarithmic a capacitance tube 103 is disposed within the end of the inner conductor and joined by means of a brass ring 101 to the terminal band 100. The small end of the outer conductor carries a cylindrical stem 108 provided at its lower with a funnel 106 surrounding the end of inlet tube 28. Liquid dielectric forced from the inlet tube into the stem 108 enters the coaxial space through holes 93, 116. A glass tube 118 mounted between the lower end of the outer conductor and the annular member 45 confines the flow of dielectric to the vicinity of the inner conductor 40. Bleed holes 128 are provided to equalize the pressure on either side of the glass tube 118. The liquid dielectric flows out through the tube 22 to a heat exchanger and pump. It is then recirculated. A detector 134 is mounted in the wall of the container 1. Specification 641,607 is referred to.