Alcatel

Alcatel N.v.

Alcatel Alsthom Compagnie Generale D'electricite

Filip Marcel Louagie

Jean-Philippe Robert Cornil

Didier Rene Haspeslagh

Zhong Yuan Chang

The invention relates to a method for selecting a sequence of cells of current sources inside a cell matrix structure of a digital-analog converter and also to the corresponding converter. Symmetries are used with regard to the centre (C) of a rectangular or preferably square matrix structure, with regard to a symmetry point (S) located at a quarter of the length of a diagonal (D1) from the centre and with regard to one of the two mean perpendiculars (M1) of the structure for selecting the mapping areas (1, 2, . . . ) for the consecutive cells.

Method for selecting a sequence of cells inside a bidimensional matrix

A low noise amplifier structure based on a Differential Difference Amplifier (DDA1) having a differential output (outp, outn) and two differential pairs of input terminals (N1, P1; N2, P2). The input signal (V.sub.IN) is applied to terminals (N2, P1) which belong to different differential pairs. In this way, none of the differential pairs receives a high input signal, and hence none of them cause unacceptable harmonic distortion. The dynamic input range is thus high. The gain of the structure is determined by a resistive circuit (R2a, R2a'; R2b, R2b') coupled to the remaining terminals (N1, P2) of the differential pairs. The common mode of these remaining terminals (N1, P2) is, independently from the output common mode, biased at the input common mode via a common mode feedback circuit (DDA2; GL1, GH1, GH3, R2a, R2a'; GL2, GH2, GH4, R2b, R2b') based on a second differential difference amplifier (DDA2). Some switching elements (GL1, GH1, GH3; GL2, GH2, GH4) allow the gain to be programmed and prevent the common mode feedback circuit from injecting differential noise if the gain is high. The structure is adapted to amplify signals of 1 Vpp with acceptably low distortion.

Low noise amplifier structure

To go from a coupled high level to a decoupled low level, a source unit (SU) of a transmitter (T) must be decoupled from a transmission line (TL) by a impedance unit (IU). As a result, oscillatory transition phenomena appear in the output signal and this signal possibly goes beyond a prescribed template. To avoid such overshoot problems the present transmitter (T) decreases the signal level during a decrease period before decoupling the source unit (SU) from the transmission line (TL). Therefore a source control circuit (SCC) is included in the control unit (CU) of the transmitter (T) for controlling the source level in such a way that the output signal level is decreasing.

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Dadizele, Belgium

Filip Marcel Louagie