Differential coder for electrical signals

1. A differential coder ( 10 ) for electrical signals, comprising:

control means ( 21 , 22 ) adapted:

to receive a clock signal (CK) defining a bit time and an input binary data signal (DATA) substantially synchronized with the clock signal and defining a sequence of first and second values (N 1 , N 2 ) in accordance with a non return to zero format, and

to supply a master control signal (A) defined by a stable level (ST) and by a change of level (P 1 to P 11 ) that is triggered when the input binary data signal corresponds to the second value, and

a bistable T controlled by the control means and adapted to supply an output binary data signal (S, S*) having a low level (Na) and a high level (Nb) and which is defined by:

the same binary state (‘0’, ‘1’) over two successive bit times when the master control signal is maintained at the stable level, and

a change of state associated with a change (C 1 to C 10 ) from either the low level or the high level to the high level or the low level triggered by said change of level, respectively

which coder is characterized in that the bistable T comprises a master bistable ( 11 ) followed by a slave bistable ( 12 ) each having a main control input (E 1 , E 2 ),

and in that the differential coder is integrated and said control means comprise:

a first circuit ( 21 ) dedicated to the master bistable and adapted to supply said master control signal (A) which is injected into the main control input of the master bistable, and

a second circuit ( 22 ) dedicated to the slave bistable, controlled by said clock signal (CK) and adapted to supply a slave control signal (CK 2 ) that is representative of a signal complementary to the clock signal and injected into the main control input of the slave bistable.

2. A differential electrical signal coder ( 10 ) according to claim 1 , characterized in that the duration of the change of level is less than or equal to the bit time and preferably substantially equal to half a bit time.

3. A differential electrical signal coder ( 10 ) according to claim 1 , characterized in that the first circuit ( 21 ) is adapted to supply a subsidiary master control signal (A*) that is either complementary to said master control signal or constant and is injected into a subsidiary control input (E 1 ′) of the master bistable and the second circuit ( 22 ) is adapted to supply a subsidiary slave control signal that is either complementary to said slave control signal (CK 2 *) or constant and is injected into a subsidiary control input (E 2 ′) of the slave bistable.

4. A differential electrical signal coder ( 10 ) according to claim 1 , characterized in that the first circuit ( 21 ) comprises an analogue comparator ( 2 ) for comparing the input binary data signal (DATA) and a clock signal (CK) and adapted to supply at least said master control signal (A).

5. A differential electrical signal coder ( 10 ) according to claim 4 , characterized in that the analogue comparator ( 2 ) comprises a differential pair comprising two transistors ( 2 a , 2 b ) voltage-controlled by the clock signal (CK) and by the input binary data signal (DATA), respectively, and adapted to supply a subsidiary master control signal (A*) that is complementary to said master control signal and is injected into a subsidiary control input (E 1 ′) of the master bistable and said second value (N 2 ) is selected from the values of the clock signal (CK).

6. A differential electrical signal coder ( 10 ) according to claim 4 , characterized in that the first circuit ( 21 ) comprises a signal amplification stage ( 3 ) downstream of the analogue comparator ( 2 ) and of similar structure to the analogue comparator.

7. A differential electrical signal coder ( 10 ) according to claim 1 , characterized in that it is based on heterojunction bipolar transistors ( 2 a to 4 b ).

8. A differential electrical signal coder ( 10 ) selected from duobinary coders, PSBT coders and DPSK coders including a precoder corresponding to the differential coder according to claim 1 .