Abstract: An embodiment of the transmission system comprises an MSK linear-modular transmitter and an MSK differentially coherent receiver connected by a transmission medium 3. A system embodying the invention is essentially characterized by filters in the receiver including analog or digital equalizers and by a differential encoding carried out on symbols of a message to be transmitted by a differential encoder included in the transmitter. The function of the equalizer is to eliminate intersymbol inteference in received signals. The differential encoding carried out is such that a coded symbol of rank k issued by the encoder depends on the corresponding symbol of the message and on the coded symbol of rank k-M, whereby M is an odd integer preferably greater than 1. On reception the probability of decision error with regard to a received symbol is all the lower that the integer M is high. The value M=3 is an appropriate value.

Abstract: A self-adaptive equalizer circuit for a receive using differential demodulation, and in particular for a receiver using a plurality of paths in diversity (1, 2). For each diversity path (1, 2) there is a self-adaptive filter (18, 19) placed before the differential demodulation. The coefficients (CO to Cn) of the filter are updated at each instant KT, where T is the symbol rate period, using the formula:Ci(k)=Ci(k-1)-.mu.. y(k-1). x(k-1)* . e(k)where .mu. is a real number much less than 1, e.g. equal to 0.001, where Ci(k) is the value given to the coefficient (Ci) at instant kT; Ci(k-1) is the value taken by the same coefficient Ci at the instant (k-1)T; y(K-1) is the output signal from the self-adaptive filter, the symbol being sampled at the symbol rate of period T; x(k-i)* is the complex conjugate value of the sample x(k-i) present in the filter at said instant kT and relating to the coefficient Ci; and e(k) is the above-mentioned error at the instant kT.