U.S. Philips Corporation

Telecommunications Radioelectriques Et Telephoniques

Jean-Pierre H Van Uffelen

Guy A David

Michel Lebourg

Alain Deconche

Jean-Pierre M Defeuilly

Daniel Robillard

A transmitting-receiving station for transmitting information by frequency hopping comprises a code generator to define the use of a plurality of channels in accordance with a high-speed skip law for a transmitting-receiving station in the stand-by mode, the high-speed skip law consisting in the use of each of the channels during a period of time Tp, while the low-speed skip law governs the change of listening channels used during N.times.Tp, each corresponding to a center channel out of a sequence of N channels of the high-speed skip law. The center channel contains a synchronizing code. The station comprises a memory device to which a write circuit for progressively storing therein the codes produced by the generator and also to which a read circuit is connected to take the codes from the memory as a function of the positions of the transmitting-receiving station.

Transmitting-receiving station for a system for transmitting data by

Fast automatic gain control (AGC) arrangement provided in an RF receiver which receives data from high-rate multiple transmission channels, in which the AGC amplifier (1) is controlled by a control voltage read from a random access memory RAM (2) which renders it possible to repeat once or several times consecutively the measurement and the correction of the output voltage of the amplifier during the period of time in which a channel is in use, the control voltage correction signal being processed in a circuit (6-10) for measuring and comparing the output voltage of the AGC amplifier to which a read-only memory (PROM)(11) is added which provides a means for correcting the imperfections of the amplifier (1) and of said measuring and comparison circuit.

Fast automatic gain control arrangement

A frequency correction method used in the receiver of a data transmission system in which a synchronizing word is transmitted before the data. During each of several steps there are calculated at least one pair of in-phase partial correlations C.sub.r (k-1), C.sub.r (k) and at least one pair of quadrature partial correlations C.sub.i (k-1), C.sub.i (k). The partial correlations of the order (k-1) and (k) in each step relate to two consecutive portions of the same length of a local synchronizing word and the samples of the received demodulated signal; the portions of a step p are greater than the portions of step p-1; the partial correction of a step p are phase-corrected by taking account of the frequency correlation calculated in step p-1. A frequency deviation is calculated from the partial correlations of each step. The final frequency correction to be retained is the sum of the frequency deviations calculated at the end of each step.

Method for correcting the frequency of a local carrier in a receiver of

This arrangement for restituting the clock is used to sample the demodulated signals formed by demodulation of the received signal by means of the signals which are in phase with and shifted through 90.degree. relative to a local carrier. The arrangement according to the invention comprises logic circuit to detect to which phase section out of n possible phase sections of the transmitted signals the phase of the received signal belongs at the sampling instants, and calculation to form the component which is in phase or shifted through 90.degree., of a signal derived from the received signal by means of a phase shift .DELTA..theta. to make its phase equal, at the sampling instants, to the center phase of the detected phase section. The zero-passages of this component are used to control the local clock.

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Chevilly Larue, France

Jean-Pierre H Van Uffelen