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Abstract

The successive symbols of a digital stream are converted into phase increments which are accumulated. A modulating phase is obtained by filtering the accumulated phase. A complex signal is produced whose argument represents the modulating phase. Two quadrature radio waveforms are respectively modulated on the basis of that complex signal, and a radio signal resulting from a combination of the two modulated waveforms is transmitted. The complex signal may be filtered digitally. Its real and imaginary components are converted into analog form, and are subjected to anti-aliasing analog filtering and then mixed with the two radio waveforms. Appropriate sizing of the digital filters provides efficient modulation with small envelope variations, causing little adjacent channel interference and a low error rate.

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First Claim