U.S. Philips Corporation

Said Moridi

Hikmet Sari

Lydie Desperben

Georges Bonnerot

Georges Martinez

Georges M Karam

A decoder for a series of received digital signal samples which are encoded as points in a 2-dimensional constellation of points corresponding to authorized code values, which constellation is sub-divided into a plurality of subsets. The branch length .mu. between a received point and the closest authorized point in a subset is calculated as a function of the magnitude and sign of the error distance between the received point and the closest authorized point of the constellation, and of the displacement between successive authorized points in the subsets. It is thus possible to determine branch length without calculation of squared values and without employing any approximations.

Transmission system using block-coded or trellis-coded modulations,

A predistortion arrangement (9) for a digital transmission system transmits complex input data of a constellation by means of a modulator (14) and a power amplifier (15) which distorts the data. The arrangement comprising a predistortion circuit (11) which predistorts the input data in opposite sense before they pass through the amplifier and a transmit filter (10) which applies oversampled filtered data encoded with 2N bits to the predistortion circuit (11) at the rate k/T. The predistortion circuit (11) is formed from an encoder (20) transforming the filtered 2N-bit encoded data into data encoded with 2M bits (M&lt;N) which address a memory (51) that stores complex predistortion coefficients, and a complex multiplier (52) that multiplies for each data element the 2N bits of the filtered data element by the selected predistortion coefficient for producing predistorted data.

Predistortion arrangement for a digital transmission system

A circuit for recovering the carrier of a digitally modulated wave having a phase symmetry 2.pi./M, wherein M is the order of the symmetry, includes means for automatic and fast acquisition comprising a voltage-controlled oscillator having an output supplying said carrier and a control input to which an error signal .epsilon.(.phi.) is applied in order to change the oscillator phase and to adjust it to the phase of the digital modulated wave. This wave is introduced in two channels, one being in phase and the other being in quadrature with the carrier, each comprising the series arrangement of: a demodulator, a low-pass filter, reconstruction means for reconstructing a signal and for determining the error between the filtered and reconstructed signals, the quadrature channel comprising in addition a 90.degree. phase shifter, the two channels being joined together with the aid of a phase comparator arrangement which produces a comparison signal and a variable-rate sampling clock. With the representation of the signals from the in-phase and quadrature channels defining the states of a signal constellation of the modulated wave, the phase comparator arrangement comprises means for selecting received signal points with the aid of zones which are centered on or eccentric to certain diagonal states of the signal constellation, and means for generating the sampling clock by eliminating from a recovered symbol clock an active edge capable of validating zero crossings of the comparator signal which do not correspond to a phase difference equal to 2k.pi./M (k and M integers).

Circuit for recovering the carrier wave in digital transmission systems

An adaptive equalizer arrangement for digital transmission system comprises at the output of the transmission channel a first in-phase path and in parallel with this first path, a second quadrature path, both paths being of the non-recursive transversal filter type having n branches and (n-1) delay circuits between the inputs of these branches, each of these n branches comprising, arranged in series, a mixer, a low-pass filter, a multiplier, and having their outputs connected to an adder which is followed by a sampling circuit and thereafter by a comparator circuit to decide the symbols to be transmitted from the outputs of these paths. The arrangement also comprises a third control path which comprises two subtracting circuits to determine the differences between the signals before and after decision and a control circuit of a voltage-controlled oscillator, 2n phase shifters and 2n multipliers.

Growing community of inventors

Paris, France

Said Moridi