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Abstract

A broad band digital radio receiver for multicarrier signals employs a quadrature demodulator to directly shift the radiofrequency signal in a base band. A local oscillator has frequency f.sub.0 placed at the center of the radiofrequency BW band, so channel pairs, symmetric versus f.sub.0, are superimposed in the lower base half-band. Base band equivocation is then solved by numeric-type second orthogonal demodulators, which supply pairs of twice-demodulated signals that can be grouped in four equation systems in four unknown values consisting of in-phase and quadrature components of the two channels of each pair. Subsequent reconstruction networks solve the relevant systems and give the two components of each single channel for each pair. One network in the receiver measures amplitude and phase dissymmetries in the two branches of the analog demodulator and supplies four corresponding digital coefficients to the reconstruction network, which can then counterbalance at output the effects of dissymmetry.

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First Claim