Fractionally-spaced adaptively-equalized self-recovering digital receiver for amplitude-Phase modulated signals

In a data receiver for a data transmission system wherein data symbols are transmitted over a transmission channel at the signaling rate 1/T, using an amplitude-phase carrier modulation technique having a data constellation, the receiver including an adaptive equalizer having several tap coefficients, a method of equalization, comprising the steps of:

• applying a signal received from the transmission channel to the equalizer, with the equalizer providing an equalized signal y.sub.n at the signaling instant nT, where the value of n ranges from zero to infinity, in accordance with the following expression:
• y.sub.n =x.sub.n 'C
• where x.sub.n is a vector of the signal stored in the equalizer at the signaling instant nT, ' denotes transposition of vector x.sub.n, C is a vector of the tap coefficient values;
• partitioning the data constellation into sub-constellations having same pattern modulo rotation and translation;
• centering each sub-constellation to the origin of the data constellation;
• generating an error signal e.sub.n derived from the equalized signal, with the error signal generated at the signaling instant nT being defined by the expression:
• e.sub.n =y.sub.n G(R-.vertline.y.sub.n -V(y.sub.n).vertline..sup.2)
• where y.sub.n is a phase-corrected signal derived from the equalized signal, G is a scaling factor, R is a constant, and V is a vector that points to the center of the sub-constellation to which y.sub.n belongs;
• and
• adjusting the tap coefficients of the equalizer so as to minimize the error signal e.sub.n.

In a data receiver for a data transmission system wherein data symbols are transmitted over a transmission channel at the signaling rate 1/T, using an amplitude-phase carrier modulation technique having a data constellation, the receiver including an adaptive equalizer having several tap coefficients, a method of equalization, comprising the steps of:

• applying a signal received from the transmission channel to the equalizer, with the equalizer providing an equalized signal y.sub.n at the signaling instant nT, where the value of n ranges from zero to infinity, in accordance with the following expression:
• y.sub.n =x.sub.n 'C
• where x.sub.n is a vector of the signal stored in the equalizer at the signaling instant nT, ' denotes transposition of vector x.sub.n, and C is a vector of the tap coefficient values;
• generating K partitions of the data constellation, where K is a positive integer, with each partition comprising sub-constellations having same pattern modulo rotation and translation;
• for each partition, centering each sub-constellation in the partition to the origin of the data constellation;
• generating an error signal e.sub.n derived from the equalized signal, with the error signal generated at the signaling instant nT being defined by the expression:
• ##EQU17## where y.sub.n is a phase-corrected signal derived from the equalized signal, G.sub.k is a scaling factor, R.sub.k is a constant, and V.sub.k is a vector that points to the center of the sub-constellation to which y.sub.n belongs;
• and
• adjusting the tap coefficients of the equalizer so as to minimize the error signal e.sub.n.

A data receiver for a data transmission system wherein data symbols are transmitted over a transmission channel using an amplitude-phase carrier modulation technique having a data constellation, comprising:

• an adaptive equalizer having several tap coefficients;
• means for partitioning the data constellation into sub-constellations having same pattern modulo rotation and translation;
• means for centering each sub-constellation to the origin of the data constellation;
• and
• means for adjusting the tap coefficients so as to minimize dispersion in the centered sub-constellations wherein dispersion is a scaled function of the weighted sum of the quadratic distance between phase-corrected equalizer output and the center of the sub-constellations.