Balanced Transmission-Line Measurements Using Coaxial Equipment (Correspondence)

The availability of commercial precision coaxial hybrids makes measurements on balanced two-conductor transmission lines as easy and as practical as on an unbalanced coaxial system. These hybrids, when used as a balun, transform an unbalanced coaxial system to a balanced shielded system and because of the nature of the balanced shielded system permit the measurement of the characteristics of loads connected thereto by the use of commercial coaxial test equipment. This technique has been successfully used from 600 MHz to 5 GHz, and with presently available components can be used at HF and VHF as well. The theory upon which the measurement technique is based is outlined and some results of an experimental verification included.