| 摘要 |
A selected length of antenna for a device under test is placed within a conductive inner cylinder, forming an unterminated "input" coaxial transmission line. The inner cylinder is in turn within and coaxial with a conductive outer cylinder, forming an "output" transmission line. The inner cylinder is the center conductor of the output transmission line, and in a region extending beyond the extent of the antenna therein, conically tapers to being a normal center conductor of solid cross section. The outer cylinder matches this taper to maintain a constant characteristic impedance Z0out (say, 50 OMEGA) for the output transmission line, which then delivers its output signal to a matched terminating load in measurement equipment via either a coaxial connector or an interconnecting length of auxiliary transmission line. These triaxially nested input and output transmission lines are supported at a driven end by an RF tight box that contains a mounting fixture to support the device under test in a fixed and appropriate relation to the triaxially nested input and output transmission lines, and that is lined with anechoic RF absorbing material.
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