System for data transmission by means of an angle-modulated carr

Details System for data transmission by means of an angle-modulated carr System for data transmission by means of an angle-modulated carr

1978-08-23

1980-10-21

Griffin, Robert L.

Pulse or digital communications

Repeaters

Testing

375 86, H04L 2718

Patent

active

042298210

ABSTRACT:
A system having a transmitter and a receiver for transmitting binary data signals of a given symbol rate, an angle-modulated carrier signal of a substantially constant amplitude and a continuous phase being generated in the modulation stage of the transmitter, and the transmitted modulated signal being orthogonally, coherently demodulated in the receiver. The modulation stage of the transmitter is arranged so that the phase of the modulated signal changes in each symbol interval by an amount from the sequence -.pi./2, -.pi./4, 0, .pi./4, .pi./2 (rad.), which amount is determined for the relevant symbol interval by at least two successive data symbols, and the value of the phase within the relevant symbol interval is determined by a filtered version of at least these two succesive data symbols. These measures result in a system which, without sacrificing the remaining desired communication properties of FFSK-systems, utilizes the available frequency spectrum in a more efficient manner than FFSK-systems, because the modulated signal has both a narrower spectral main lobe and, for frequencies outside this spectral main lobe, considerably less power than the FFSK-signal. Consequently this system is very well suited for efficient data transmission over radio links.

REFERENCES:
patent: 3818378 (1974-06-01), Phillips
patent: 3916313 (1975-10-01), Lowry
patent: 3993868 (1976-11-01), Balcewicz
patent: 4109101 (1978-08-01), Mitani

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