GB356323A - Improvements in or relating to modulating systems - Google Patents

Abstract

356,323. Phase-changing telephone currents. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.-(Assignees of Plebanski, J.; 32, Wspolna, Warsaw.) June 14, 1930, No. 18299. Convention date, July 10, 1929. [Class 40 (iv).] In a system of single side-band radio transmission, speech currents with all their frequency components equally displaced in phase are required at the transformers T1, T2. This phase displacement is effected without the use of balanced modulators by first modulating a carrier D1 by the valves M1, a, selecting a single side-band by the filter F, and then de-modulating this side-band by combining it in the valve d with the same carrier D1 displaced the required angle (say 90‹) in phase. The side-band filter F may comprise an artificial line L, R, Fig. 2, coupled at various points through tuned circuits to the input circuit of a valve V. By suitable tuning of these circuits all the frequencies passed by the filter will have approximately the same displacement in phase. The tuned circuits may be directly connected to tappings on the line L, and resistances r can be inserted in the grid circuit of the valve or in the tapping-leads, Figs. 4 and 5 (not shown). The tuned circuits may be mutually coupled. The tuned circuits may feed into a second artificial line, F:g. 6 (not shown), or into a tuned grid circuit, Fig. 7 (not shown). Specifications 211,151, 283,190, 297,253, and 301,352, [all in Class 40 (v), Wireless signalling &c.], are referred to.