Modulation device with input signal modification for correction

Details Modulation device with input signal modification for correction Modulation device with input signal modification for correction

1990-12-21

1992-03-03

Mis, David

Modulators

Phase shift keying modulator or quadrature amplitude modulator

375 58, 375 60, H03C 308, H03K 710

Patent

active

050936379

ABSTRACT:
In a modulation system using an amplitude and a phase of a carrier wave as information such as a QPSK system, a modulation device modifies an input signal series to compensate the nonlinear characteristics of an amplifier located at a later stage, and provides a carrier wave modulated by the modified signal series to the amplifier. A first arithmetic circuit obtains an amplitude and a phase of an input signal by calculation. A ROM is set with correction data corresponding to the calculated amplitude so as to compensate the nonlinearity of the amplifier. A modification value generating circuit and a RAM output an amount of compensation so as to further modify the correction data according to part of an output signal from the amplifier to compensate amplifier characteristic changes due to temperature variations and the like. A second arithmetic circuit provides a signal series produced from the modified amplitude and phase to a quadrature modulator.

REFERENCES:
patent: 4787094 (1988-11-01), Eguchi

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