U.S. Philips Corporation

Michel Lebourg

Gilbert Petitjean

Jean-Pierre H Van Uffelen

Benoit Gelin

Christian Le Tortorec

Daniel Robillard

The method ensures the coherent demodulation by digitally processing a continuous-phase modulated signal (for instance, of the GMSK type). The received signal is transposed in the baseband, converted into a digital signal and transferred to a signal processor. Each transmitted data packet has a known preamble sequence of N bits which allows for approximate estimation of the frame-synchronization and the bit-synchronization and also the initial phase and the residual frequency offset. The progressive refinement of the estimation is obtained with two interleaved digital loops: a slow loop for detecting the bit-synchronization and a fast loop effecting intermediate decisions over additional blocks of bits for the estimation of the initial phase and the residual frequency offset.

Coherent demodulation method for a digitally modulated signal having a

A variable attenuation device intended to be inserted between a transmitter circuit having a certain internal impedance and a load circuit; it composed of at least on parallel attenuation branch made up from a variable resistance component (in particular a p-i-n diode) and a bias circuit to vary the resistance of the component as a function of an attenuation control variable. The parallel attenuation branch has a limiting component which is connected in series with the variable resistance component and whose value ensures the matching of the internal impedance of the transmitter circuit.

Variable attenuation device intended to be inserted between a

A device for marking, for example, the position of a control knob, comprising an arrangement with several terminals each of which corresponds to one of the positions, the application of a DC voltage (+V) at each instant to one and only one of the terminals indicating the presence of the knob in the corresponding position. The device includes a series of operational amplifiers having specified gain, each amplifier having its inverting input connected to one of the terminals and its non-inverting input connected to the terminal corresponding to the next position. Each terminal is connected to a circuit for taking those terminals, which do not correspond to the momentary position of the knob, to a specified voltage. The outputs of the amplifiers are connected to a detection circuit for detecting on one of them any transition whose amplitude exceeds a specified threshold and to control a count-up/count-down device whose output value is incremented or decremented depending on the direction of the transition, this output value constituting an indication of the position of the knob.

Encoding device for multiple consecutive position detection

A PIN diode is in series in a high-frequency signal path between an input and an output, and is controllably biased either on or off by a control signal supplied thereto from the output of a control circuit in response to a command voltage. The control circuit derives the control signal from a positive voltage source when the diode is to be turned on and from a negative voltage source when the diode is to be turned off. The negative voltage must be a relatively high value, which can cause excessive power dissipation in the control circuit due to charging of the bypass capacitance present at the output terminal thereof for shunting high frequencies. To prevent that, the control circuit includes an overvoltage circuit which produces a short duration trigger pulse in response to change-over from the positive voltage source to the negative voltage source and which supplies a current pulse of brief duration for charging the bypass capacitance.

Interrupter arrangement for high-frequency signals

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.

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Clamart, France

Michel Lebourg