GB1126788A - Single side-band carrier systems - Google Patents

Abstract

1,126,788. Single sideband modulation; multiplex carrier systems. COMMUNICATIONS CONSULTANTS Ltd. 31 Aug., 1967 [22 July, 1966], No. 33137/66. Headings H3R and H4R. A single sideband modulator of the type comprising means (48, Fig. 2) for splitting an input signal into two quadrature components, means (54) for splitting a carrier wave into two quadrature components, two balanced modulators 50 and 52 fed with the quadrature input and carrier signals, and means (56) for combining the outputs of the balanced modulators, is characterized in that the balanced modulators comprise diodes and resistances (72, Fig. 3, not shown) and are constructed as an integrated circuit with the other units mentioned above. The output means 56 is preferably an FET amplifier, and the phase splitting unit 48 may be preceded by a filter 44 and an FET amplifier 46. Fig. 2 shows a multiplex telephone system wherein the carrier for the first channel is provided from a master oscillator 40 which also feeds a network 42 of dividers, filters and multipliers, this network providing 11 other carrier waves at 4 kc./s. intervals. The 64 kc./s. signal from oscillator 40 is transmitted as a pilot signal and recovered at the receiver by a filter 66 and supplied to unit 68 which re-generates the required carrier waves at the receiver. In Fig. 2, the components fed to the modulators 50A and 52A in the second channel are such that the output from the channel is in phase quadrature with the output from channel 1; similarly channel 3 is in phase quadrature with channel 2, so that cross-talk is reduced. As an alternative, Fig. 4 (not shown), each sideband may comprise two quadrature components carrying different information signals thereby doubling the number of channels in a given bandwidth.