GB670023A - Improvements in or relating to radio communication systems - Google Patents

Abstract

670,023. Multiplex radio signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 2, 1950 [Feb. 23, 1949], No. 4988/49. Class 40 (v). The signals from two channels modulate different transmitters using the same carrier frequency, one of which radiates an omnidirectional field, and the other of which feeds spaced aerials in anti-phase which produce a field containing adjacent regions of opposite phase. A receiver may be designed to receive one or other or both of the channels without mutual interference. The master oscillator 4, Fig. 1, drives two transmitters 5, 6, each having a modulator 7, 8 respectively. The transmitter 5 feeds a single vertical aerial 1 and the transmitter 6 a pair of vertical aerials 2, 3 in line with aerial 1 and each spaced a number of wavelengths, for example ten, from aerial 1. The aerials 2, 3 are energized at equal amplitudes and in opposite phase through non- radiating lines 11, 12 and phase and amplitude equalizing networks 13, 14 respectively. A receiver adapted to reproduce the signals from both channels, comprises two similar vertical spaced loop aerials 15, 16, Fig. 4, positioned on a line at right angles to the direction of the transmitter and so spaced as to pick up signals of opposite phase from the field due to aerials 2, 3 at the transmitter. The aerials 15, 16 feed cathode follower stages V1, V2, through non-radiating lines F2, Fl respectively, and the outputs of stages V1, V2 are combined in parallel in stages V3, V4 to feed receiver T1 and in push-pull in stages V5, V6 to feed receiver T2, so that receiver T1 is only responsive to the transmission from aerial 1 and receiver T2 to the transmission from aerials 2 and 3.