Apparatus for correcting quadrature error in a modulator and/or in a demodulator for a signal having a plurality of phase states, a corresponding transmitter, and a corresponding receiver

Apparatus for correcting quadrature error in a modulation stage (1) to which a digital-type modulating signal is applied, the signal being constituted, at each symbol time, by a symbol of a constellation having a plurality of phase states or of amplitude and phase states, each symbol of said constellation being determined by two amplitude levels P and Q;

• said apparatus being characterized in that it comprises processing means (51) supplying two corrected amplitude levels P' and Q' on the basis of said amplitude levels P and Q, said corrected amplitude levels P' and Q' being applied to said modulation stage (1) and being respectively equal to the values in any one of the following pairs of values:
• P+Q and Q-P
• P+Q and P-Q
• -P-Q and Q-P
• -P-Q and P-Q
• Q-P and P+Q
• P-Q and P+Q
• Q-P and -P-Q
• P-Q and -P-Q.

A receiver for receiving signals, each of which has a plurality of phase states or of amplitude and phase states, said receiver being characterized in that it includes apparatus for correcting quadrature error in a demodulation stage supplying a digital signal constituted, at each symbol time, by a symbol of a constellation having a plurality of phase states or of amplitude and phase states, each symbol of said constellation being determined by two amplitude levels P and Q output by said demodulation stage, said apparatus being characterized in that it comprises processing means supplying two corrected amplitude levels P' and Q' on the basis of said amplitude levels P and Q, said corrected amplitude levels P' and Q' being respectively equal to the values in any one of the following pairs of values:

• P+Q and Q-P
• P+Q and P-Q
• -P-Q and Q-P
• -P-Q and P-Q
• Q-P and P+Q
• P-Q and P+Q
• Q-P and -P-Q
• P-Q and -P-Q.

A transmitter for transmitting signals, each of which has a plurality of phase states or of amplitude and phase states, said transmitter being characterized in that it includes apparatus for correcting quadrature error in a demodulation stage supplying a digital signal constituted, at each symbol time, by a symbol of a constellation having a plurality of phase states or of amplitude and phase states, each symbol of said constellation being determined by two amplitude levels P and Q output by said demodulation stage, said apparatus being characterized in that it comprises processing means supplying two corrected amplitude levels P' and Q' on the basis of said amplitude levels P and Q, said corrected amplitude levels P' and Q' being respectively equal to the values in any one of the following pairs of values:

• P+Q and Q-P
• P-Q and P-Q
• -P-Q and Q-P
• -P-Q and P-Q
• Q-P and P+Q
• P-Q and P+Q
• Q-P and -P-Q
• P-Q and -P-Q.