The Use of Coaxial and Balanced Transmission Lines in Filters and Wide Band Transformers for High Radio Frequencies

A T the higher radio frequencies, coil and condenser networks become difficult to construct on account of the small sizes of the elements and the large effects of the interconnecting windings. The Q realizable in high-frequency coils is about the same as can be obtained at the lower frequencies but due to the smaller percentage band widths, it is desirable to obtain a higher Q. There has been a tendency to replace coils by small lengths of transmission lines, and these have been used to some extent as tuned circuits, and as single-frequency transformers.1,2,3 It is the purpose of this paper to describe work which has been done in constructing selective filters and wide-band transformers from lengths of transmission lines and condensers. Due to the high ratio of reactance to resistance obtainable in both of these types of elements, 1 "Transmission Lines for Short-Wave Radio Systems," E. J. Sterba and C. B. Feldman, B. S. T. J., Vol. X I , N o . 3, July 1932, page 411. 2 " R e s o n a n t Lines for Radio Circuits," F. E. Terman, Elec. Engg., Vol. 53, pp. 1046-1053, J u l y 1934. 3 "A Unicontrol Radio Receiver for Ultra-High Frequencies Using Concentric Lines as Interstage Couplers," F. W. Dunmore, Proc. I. R. E., Vol. 24, No. 6, June 1936. 275