Etablissement Public De Diffusion Dit 'telediffusion De France'

Centre National D'etudes Des Telecommunications

Etablissement Public De Telediffusion Dit

Jacques Veillard

Daniel Pommier

Jeannine Le Goff Epouse Henaff

A receiver is provided for a television system which uses time division miplexing (TDM) of analog image signals and of bursts of duobinary coded digital data signals. The digital data signals are transmitted during the line and frame blanking intervals and grouped together in packets, comprising the sound and synchronization signals, the spectral width required by the analog part being greater than that required by the digital part. The receiver comprises a common frequency demodulator for the analog and digital signals, adaptive as a function of the signal-to-noise ratio after demodulation as a width less than the width which is optimum for the analog part when the latter has a high signal-to-noise ratio. The demodulator has an input filter which is either analog or digital and may be adjusted in response to the error rate.

Frequency demodulator for television receiver with time multiplexing

A digitally modulated carrier modulated by phase shift keying or frequency shift keying with phase continuity, transmitted as useful bursts distributed at equal time intervals with phase continuity from each burst to the next burst. The carrier frequency is recovered by squaring the carrier for obtaining a spectrum and selecting the carrier frequency within said spectrum. Bursts at an acquisition frequency having the same frequency as the carrier, having a time duration longer than the time duration of the useful bursts and having characteristic features which are particular to said acquisition burst, are sent at times which are separated by time periods having a duration which is longer than the repetition period of the useful bursts by at least an order of magnitude. The acquisition bursts are received along with the useful bursts and squared to provide an acquisition spectrum. A frequency which is double of the carrier frequency is selected within the acquisition period by identifying the characteristic feature of the acquisition bursts.

Method and device for coherent demodulation of a digitally modulated

The circuit comprises a surface acoustic wave device. On the substrate (32) f the surface acoustic wave device, are provided two pairs of input transducers (33, 34, 35, 36) connected, in parallel, to the input of the circuit. The transducers (33, 34, 35, 36) initiate surface acoustic waves corresponding to the signals applied on two pairs of paths (41, 42, 43, 44) ending at two pairs of reception transducers (37, 38, 39, 40). The outputs of the output transducers of the first pair (37, 38) are connected to the two inputs of a mixer (28) whose output yields the received digital signal. The outputs of the second pair of transducers (39, 40) are connected to the inputs of two limiters (26, 27) whose outputs are connected to the two inputs of a mixer (29) whose output yields the analog signal. The difference in path lengths of the first pair (41, 42) introduces a delay of the order of one bit and the difference in path lengths of the second pair (43, 44) introduces a delay equal to the inverse of twice the bandwidth between the peaks of the discriminator thus constituted.

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Saint Gregoire, France

Jacques Veillard