GB617092A - Improvements in attenuators for use with wave guides - Google Patents

Abstract

617,092. Attenuators. WESTERN ELECTRIC CO., Inc. March 28, 1946, No. 9663. Convention date, March 30, 1945. Addition to 576,145. [Class 40 (viii)] A wave-guide attenuator of the kind described in the parent Specification comprises two resistive elements longitudinally positioned opposite each other within the section of wave-guide at distances from the respective sides of the guide so related that the attenuation has a minimum variation over a selected range of frequencies. The resistive elements are in the form of vanes 2, 3 pointed at the ends to reduce reflection and mounted parallel to the narrow walls 4 of a wave-guide section 1. The elements are mounted on rods 6 which pass freely through sleeves 9 dimensioned to reduce loss of energy, and are held at the ends in slots 11 in yokes 12 which are arranged to slide but not rotate due to interengaging parts 14, 16. Each yoke 12 is connected to an arm 18 slidable in a groove on the upper surface of the guide. The arms 18 are urged inwards by springs 25 so that the ends of extensions 22 engage the peripheries of respective cams 23, 24 rotatable by a spindle 26 carrying a scale 27. Rotation of spindle 26 thus causes elements 2, 3 to move together either towards or away from the guide walls. The cams 23, 24 are so dimensioned that the elements are always at different distances from the guide walls. This gives a linear relation between attenuation and rotation of scale 27 over a considerable range of frequency. In a modification, the above effect can be obtained over a limited range of frequency and attenuation by fixing one of the vanes and moving the other.