Design of Broadband Ununs With Impedance Ratios Less Than 1:4

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  • Author: Sevick
The first appearance of the broadband transmission line transformer occurred in 1944, in a paper pub-lished by George Guan-ella [1] in the Braun-Boveri Review. In that paper, he expounded the principles of this broadband impedance matching device and is considered the inven-tor. His goal was to design a broadband balun (balanced-to-unbalanced) for the HF band, matching the balanced impedance of 960 ohms in a vacuum tube amplifier to the unbal-anced impedance of a 60 ohm coaxial cable; a 16:1 ratio. Since he did not have the magnet-ic materials of today he was unable to reach his goal. Even today it is a formidable task.