U.S. Philips Corporation

Georges Martinez

Jean-Michel Guillaud

Said Moridi

Nicolas Chauve

A frequency synthesizer SYNT intended to supply an output signal Sout having an output frequency which depends on the average frequency, referred to as symbol frequency, of an input signal Sin beset with a strong phase noise. This synthesizer SYNT includes: a phase/frequency detector PHD comparing the symbol frequency with a predetermined fraction of the output frequency, and supplying a control signal; a low-pass filter LPF filtering the control signal; and an oscillator VCO supplying a signal Sout with a frequency which is adjusted by the filtered control signal Cs. Reference pulses having the symbol frequency are generated within the synthesizer SYNT by means of pulses from an internal clock, which pulses are validated by active states of the input signal Sin.

Programmable frequency synthesizer having a low sensitivity to phase

A digital transmission system including synchronizing circuits for estimating and compensating for errors between a local oscillator signal and an input signal. The synchronizing circuits include a phase/frequency detector and correction circuit for correcting errors in an unlocked mode, and a phase detection and correction circuit for correcting errors in a locked mode. Requests for changing the synchronization circuits from the locked mode to the unlocked mode are implemented by state control circuits only after application of at least one decision condition. The state control circuits may also save and restore specific adjustments responsive to the decision condition.

Digital transmission system comprising decision means for changing the

Circuit for multiplying data in accordance with a Booth algorithm, in which the coding of the control signals is adapted to the characteristics of symmetry of a trigonometric function. The values of the function which relate to a single quadrant are stored in a memory and a converter unit makes it possible to utilize the circuit whatever the quadrant. The values of the trigonometric function may be obtained through interpolation. Application to the calculations of Fourier transforms or DCT transforms.

Booth multiplier for trigonometric functions

Digital transmission system (10) for digitally modulated signals, comprising a receiving device (14) which includes a demodulator (110), processing apparatus (120) and carrier synchronizing apparatus (16) for estimating and compensating for synchronization errors. The synchronizing apparatus includes a first loop (1) for phase/frequency correction and a second loop (2) for phase correction, the operation of these loops being controlled by a mode detector (130) depending on whether the receiving device is seeking to unlock or lock. The second loop (2) transforms a phase error signal into a phase correction signal which is mixed in mixer (246) with the signal coming from the demodulator. Preferably, the signals are modulated via a coded modulation.

Receiver with two synchronization loops

A decoder for a series of received digital signal samples which are encoded as points in a 2-dimensional constellation of points corresponding to authorized code values, which constellation is sub-divided into a plurality of subsets. The branch length .mu. between a received point and the closest authorized point in a subset is calculated as a function of the magnitude and sign of the error distance between the received point and the closest authorized point of the constellation, and of the displacement between successive authorized points in the subsets. It is thus possible to determine branch length without calculation of squared values and without employing any approximations.

Transmission system using block-coded or trellis-coded modulations,

Automatic gain control circuit comprising amplifier means (10) which produce an output signal that has an amplitude controlled by a control signal (CT). Recursive filter apparatus (20) (22) measures the power of the output signal and yield a measure of power which is compared (24) with a window of permitted power values to generate the control signal (CT). Depending on the result of the comparison, an initialization signal (INI) is transmitted which enforces a reference power value on a recursive filter to accelerate the gain control. Utilization in apparatus that use signals that have fast and considerable amplitude variations, as in digital modulation signal receivers.

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Caen, France

Georges Martinez