Abstract: A process for simultaneously measuring the propagation characteristics of a plurality of radio-frequency channels. According to the invention, from several base stations are transmitted signals whose spectra are interleaved. At the receive end, each of these spectra may be reproduced and the impulse response of each channel may be calculated. Application to radio-communications with mobiles.

Abstract: A method of representing the effects on a received signal of a radio communications channel having L paths with a reduced computational effort is achieved by transforming a representation of the channel into a simplified representation. Each path of the radio communications channel has an average attenuation and a pre-determined respective delay. The received signal includes a combination of correlated components determined from an effect of pulse shaping filters on the received signal, each component being correlated with respect to each of the other components represented by a plurality of correlation coefficients. The method comprises generating a plurality of complex zero mean gaussian random variables each having a pre-determined variance, and summing the variables, to form a representation of the signal received via the radio communications channel.

Abstract: Definition takes place of a sliding window of width Ne times the sampling period (Te); for each sliding window calculation takes place of the sum of the elementary powers of the correlation samples located in said window; determination takes place of the window for which the sum of the powers is at a maximum, the synchronization then being defined by the position of the synchronized window on the window having the maximum power sum and by the rank of each correlation sample within said window.

Abstract: A process for improving the reception quality of a Code Division Multiple Access (CDMA) signal that judiciously distributes reference symbols between two CDMA signal components, namely an in phase component (I) and quadrature component (Q). The reference symbols are distributed in only one of the two components, namely the I or Q component. To further improve the reception quality, the pseudo-random spreading sequence used for one of the components is different from the pseudo-random spreading sequence used for the other component. The applications of this process include mobile land radio communications.

Abstract: A method of digital differential demodulation if which the signal to be demodulated is over sampled at a rate double the rate of the elements of the spread sequence, the products of a current sample and the preceding conjugated sample are calculated and these products are summed, possibly weighting them, in a window covering at least a part of the period of the information symbols, the real part of this sum is taken in order to obtain a decision sample used to reconstruct the information. The method is applicable to multiple access type transmissions with code division.

Abstract: A modulator in which an input train of digital pulses is encoded to produce two encoded trains of digital pulses which are used to respectively modulate two out of phase carrier components. The two modulated carrier components are combined to produce a modulated output signal. A demodulator recovers carrier and clock signals from the modulated signal and combines these with the modulated signal to recover the input train of digital pulses.

Abstract: A phase shift binary modulator which is less sensitive to the non-linear characteristics of the transmission channel. The modulator comprises a first input to which a succession of binary bits are applied, prior to their modulation and transmission. Another input receives a clock signal at the bit rate of the succession of bits applied to the first input terminal, which is, in turn, connected to an input of a first exclusive OR gate, the output of which is connected to an input of another exclusive OR gate. The output of the other OR gate is connected to the input of a flip-flop. An output of the flip-flop is connected to the second input of the first OR gate. The clock signal drives a divider, the inverse output of which is connected to the second input of the other OR gate. The direct output of the divider is connected to an input of an AND gate. The second input of the AND gate is connected to the output of a delay circuit. The binary modulator may have either four or eight phase-shift displacements.

Abstract: A four stage phase displacement modulator has a numerical signal generator with four outputs, which respectively deliver four signals, each signal having a frequency which is equal to the carrier frequency. The respective phases of the four stages are 0, .pi./2, .pi., and 3 .pi./2, which respectively appear at four inputs of a encoding device. In addition, the encoding device has two governing inputs which respectively receive two successions of impulses which constitute the modulating signal. The output of the encoding device is connected to the input of a band-pass filter, the output of which delivers the four phase modulated signal. The encoding device has a validation input to which is coupled the output of a monostable flip-flop driven by a clock signal at the rhythm of pairs of binary bits applied to the encoding device. Variable capacitors adjust the dephasings between the delivered signals.