GB1356179A - Amplitude-modulated eight-phase phase-modulated system - Google Patents

Abstract

1356179 Digital transmission: phase and amplitude modulation KOKUSAI DENSHIN DENWA KK 13 Aug 1971 [14 Aug 1970] 38156/71 Heading H4P In a phase displaced modulation system having one set of four phase orthogonal vectors displaced 45 degrees from a second similar set, each vector representing one of eight combinations of three bits, one set is amplitude modulated by a 6db with respect to the other. In one arrangement eight rectangular waves are derived from a carrier by division the relevant one being selected according to the respective states of three bit combinations. In an alternative arrangement phase shifting is performed by phase shifting circuits connected in cascade each shifter being controlled by one bit. One of the bits also controls an attentuating circuit (see Fig. 11A, not shown). A matrix in combination with gates may be employed to select the relevant wave. The receiver may comprise phase detectors 21 integrators 22 polarity detectors 23, full wave rectifiers 24, voltage comparators 25, and AND gate 26 all feeding into logic circuit 27, the phase detectors receiving inputs through phase shifters 28a, 28b, 29 from a common reference wave 131. A received wave 130 is detected at 21 and integrated at 22, the outputs 135-138 from which correspond to vectors x, y, a, b (see Fig. 13, not shown) which are detected at 23 and as the outputs 142-145 have one of two states, the eight possible conditions are detected in logic circuit 27 to produce an output of three bits. Approximately half of the components of Fig. 14 may be eliminated by incorporating an adding and subtracting circuit (30) as described with reference to Fig. 15 (not shown) the theoretical justification being included in the Specification.