GB491103A - Improvements in or relating to electrical frequency changing apparatus - Google Patents

Abstract

491,103. Modulating systems. GENERAL ELECTRIC CO., Ltd., and LEY, D. A. April 12, 1937, No. 10385. [Class 40 (v)] In electric modulators or demodulators employing non-linear elements which have a resistance-voltage characteristic substantially linear over some finite portion on which they operate, suppression of many undesired products of modulation is obtained by suitable proportioning of the circuit elements. In a single mesh containing only one rectifier, the total series resistance Ro, excluding that of the non-linear element, in the circuit, is made equal to the resistance R<1> of the element at the mean voltage applied across it. When the circuit comprises two meshes in a balanced arrangement as shown, the inputs 1 and 4 being additive in mesh a and subtractive in mesh b, the following relationship is satisfied: where ka, kb respectively are the slopes of the linear portions of the resistance-voltage characteristics of the rectifiers 10, 11, in meshes a and b. Resistances 12, 13, are employed for fine adjustment of the ratios, and decoupling networks and attenuators 2, 3, 5, 6, 7, 8, are adjusted so that the current in the output circuit 9 is proportional to the difference between the products of external resistance Ro and operating current for each mesh. In addition to the above requirements, each separate mesh may conform to the requirement first stated for a single mesh. A modulator containing four meshes wherein the carrier and signal voltages applied to one pair are equal to, but reversed in phase compared with those applied to the other pair, is considered as a duplication of the balanced circuit already discussed, and similar relations to those already stated are maintained between each mesh of a pair and each pair of meshes. Specification 472,816 is referred to.