Device and method for a wireless transmitter

1. A method for controlling a signal envelope shape of a modulation pulse in a driver of a wireless transmitter, the method comprising:

supplying a first voltage to the driver during a non-modulated state;

supplying a second voltage configurable by a configurable modulation index value to the driver during a modulated state;

switching between the non-modulated state and the modulated state, the switching comprising setting the modulation index value to configure the second voltage at a same level as the first voltage, and then switching between supplying the first voltage to the driver and supplying the second voltage to the driver; and

filtering, to a limited bandwidth, variations of the second voltage resulting from configuring the modulation index value.

2. The method according to claim 1 , wherein supplying the second voltage to the driver during the modulated state comprises setting the modulation index value to configure the second voltage at a level of a modulated carrier signal during a duration of the modulation pulse.

3. The method according to claim 1 , wherein switching between the non-modulated state and the modulated state is responsive to a state control signal and setting the modulation index value is responsive to an index control signal.

4. The method according to claim 1 , wherein supplying the second voltage comprises indexing the first voltage with the configurable modulation index value.

5. The method according to claim 1 , wherein filtering the variations of the second voltage comprises using a capacitor coupled to an output of the second voltage.

6. The method according to claim 1 , wherein filtering the variations of the second voltage comprises using an internal programmable resistive-capacitive circuit coupled to an input indexing a reference voltage by the modulation index value.

7. The method according to claim 1 , wherein filtering the variations of the second voltage comprises setting the modulation index value using at least one intermediate modulation index value before using a final modulation index value.

8. The method according to claim 1 , further comprising performing wireless communications according to at least one of the following standards: ISO14443 TypeA; ISO14443 TypeB; ISO15693; or JIS.X.6319.

9. A wireless transmitter comprising:

a first voltage supply configured to supply a first voltage to a driver during a non-modulated state;

a second voltage supply configured to supply a second voltage configurable by a modulation index value to the driver during a modulated state;

the driver, configured to controlling a signal envelope shape of a modulation pulse;

a control circuit configured to switch the driver between the non-modulated state and the modulated state, by setting the modulation index value to configure the second voltage at a same level as the first voltage and then switching between the first voltage supply and the second voltage supply supplying the driver; and

a filtering circuit configured to filter, to a limited bandwidth, variations of the second voltage resulting from setting the modulation index value.

10. The wireless transmitter according to claim 9 , wherein the first voltage supply comprises a first low drop out voltage regulator, and the second voltage supply comprises a second low drop out voltage regulator.

11. The wireless transmitter according to claim 9 , wherein the control circuit is configured to set the modulation index value to configure the second voltage at a level of a modulated carrier signal during a duration of the modulation pulse.

12. The wireless transmitter according to claim 9 , wherein the control circuit is configured to generate a state control signal and an index control signal, the driver is configured to switch supply connection between the first voltage supply and the second voltage supply responsive to the state control signal, and the second voltage supply is configured to set the modulation index value responsive to the index control signal.

13. The wireless transmitter according to claim 9 , wherein the second voltage supply is configured to index the first voltage with the modulation index value to supply the second voltage.

14. The wireless transmitter according to claim 9 , wherein the filtering circuit comprises a capacitor coupled to an output of the second voltage supply.

15. The wireless transmitter according to claim 9 , wherein the second voltage supply includes an input configured to receive a reference voltage, and is configured to index by the modulation index value the reference voltage, and the filtering circuit comprises an internal programmable resistive-capacitive circuit coupled to the input of the second voltage supply.

16. The wireless transmitter according to claim 9 , wherein the control circuit is configured to set at least one intermediate modulation index value before setting a final modulation index value.

17. The wireless transmitter according to claim 9 , wherein the wireless transmitter is configured to perform wireless communications according to at least one of the following standards: ISO14443 TypeA; ISO14443 TypeB; ISO 15693; or JIS.X.6319.

18. The wireless transmitter according to claim 9 , wherein the wireless transmitter is an integrated circuit.

19. The wireless transmitter according to claim 9 , wherein the filter circuit is configured to filter the variations of the second voltage using an internal programmable resistive-capacitive circuit coupled to an input indexing a reference voltage by the modulation index value.

20. The wireless transmitter according to claim 19 , wherein the filter circuit is configured to filter the variations of the second voltage using at least one intermediate modulation index value before using a final modulation index value.