Bell Telephone Laboratories

American Telephone and Telegraph, Co.

Howard C Reeve, Iii

Walter Debus, Jr

Curtis A Siller

A technique is presented for simplifying the recovery of two synchronous data signals having a common symbol rate after each signal has respectively modulated a different one of a pair of quadrature-related carrier signals. In the transmitter, the data signal which modulates one of the quadrature-related carrier signals is delayed relative to the data signal which modulates the other quadrature-related carrier signal. This delay is related to an IF frequency chosen at the receiver. After passing through a noisy transmission channel, the quadrature-related carrier signals are coupled in the receiver to a serial combination of an equalizer and analog-to-digital converter. This combination outputs multiple, substantially distortion-free samples of the data signals each symbol interval. The two data signals are then recovered by selecting a subset of the samples provided each symbol interval.

Simplified recovery of data signals from quadrature-related carrier

A technique for digitally synthesizing the amplitude modulation of one or more carrier signals with a random digital data signal is disclosed. Pursuant to the present invention, a memory unit is addressed by a plurality of binary coded digital symbols in the data signal. For each address, at least two digital representations are read out. Each representation corresponds to a different sample of the carrier signals which has been amplitude modulated by a composite of the spectrally shaped data signal. The disclosed technique can be adapted to synthesize a variety of modulation formats, and can provide compensation for fixed in-rail and cross-rail distortions.

Technique for synthesizing the modulation of a time varying waveform

A technique for decoding a vestigial sideband signal formed from a double-sideband signal having modulated quadrature-related carrier signals is disclosed. Within the receiver, the vestigial sideband signal is demodulated into a pair of received signals. Each of these received signals comprises a data signal which has been distorted by the double-sideband to vestigial sideband transformation. Pursuant to the present invention, each data signal is recovered in response to the associated received signal and the other data signal. Advantageously, the disclosed technique reduces the bandwidth required to transmit a given amount of information in systems which transmit modulated quadrature-related carrier signals.

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Methuen, MA, United States of America

Howard C Reeve, Iii