Selecting modulation and amplification in a transmitter

1. A transmitter for transmitting signals, comprising:

a modulator for modulating a data signal, the modulator being capable of modulating the data signal according to any of two or more modulation schemes to form a modulated signal;

an amplification arrangement for amplifying the modulated signal with any of two or more levels of gain; and

a control system configured to interdependently select one of the modulation schemes and one of the levels of gain, and to control the modulator to adopt the selected modulation scheme and to control the amplifier to adopt the selected level of gain,

wherein the control system is capable of operation in a first mode in which it is restricted to selecting a subset of combinations of the available modulation schemes and available levels of gain, which subset excludes the combination of one modulation scheme and levels of gain greater than a threshold and includes the combination of that modulation scheme and levels of gain below that threshold, and includes the combination of one other modulation scheme and levels of gain above that threshold.

2. A transmitter as claimed in claim 1 , wherein the control system is capable of operation in one or more modes in which it is restricted to selecting a respective subset of combinations of the available modulation schemes and available levels of gain.

3. A transmitter as claimed in claim 1 , wherein the amplification arrangement includes two amplifiers and the control system is arranged to control the amplification arrangement to provide levels of gain below the threshold by means of a first one of those amplifiers and to provide levels of gain above the threshold by means of both of those amplifiers.

4. A transmitter as claimed in claim 3 , wherein the first one of the amplifiers is implemented on a common integrated circuit with the modulator.

5. A transmitter as claimed in claim 1 , wherein the control system is capable of operation in a second mode in which it is restricted to selecting a subset of combinations of the available modulation schemes and available levels of gain, which subset excludes the combination of any of the modulation schemes with levels of gain greater than a threshold.

6. A transmitter as claimed in claim 5 , wherein the amplification arrangement includes two amplifiers and the control system is arranged to control the amplification arrangement to provide levels of gain below the threshold by means of a first one of those amplifiers and to provide levels of gain above the threshold by means of both of those amplifiers.

7. A transmitter as claimed in claim 6 , wherein the first one of the amplifiers is implemented on a common integrated circuit with the modulator.

8. A transmitter as claimed in claim 1 , wherein the transmitter is a radio transmitter.

9. A transmitter as claimed in claim 1 , wherein the control system is responsive to a power control signal to select one of the modulation schemes and one of the levels of gain.

10. A transmitter as claimed in claim 1 , wherein the control system is capable of adopting any of two or more algorithms for selecting one of the modulation schemes and one of the levels of gain.

11. A transmitter as claimed in claim 10 , wherein the control system is configured to adopt one of the said algorithms under the control of a user.

12. A transmitter as claimed in claim 10 , wherein the control system is configured to, when communicating with a receiver, adopt one of the said algorithms under the control of the receiver.

13. A transmitter as claimed in claim 10 , wherein the control system is factory-configured to adopt one of the said algorithms.

14. A transmitter for transmitting signals, comprising:

a modulator for modulating a data signal, the modulator being capable of modulating the data signal according to any of two or more modulation schemes to form a modulated signal;

an amplification arrangement for amplifying the modulated signal with any of two or more levels of gain; and

a control system configured to select one of the modulation schemes and one of the levels of gain, and to control the modulator to adopt the selected modulation scheme and to control the amplifier to adopt the selected level of gain, the control system being configured for operation in:

a first mode in which it is restricted to selecting a subset of combinations of the available modulation schemes and available levels of gain, which subset excludes the combination of one modulation scheme and levels of gain greater than a threshold and includes the combination of that modulation scheme and levels of gain below that threshold, and includes the combination of one other modulation scheme and levels of gain above that threshold; and

a second mode in which it is restricted to selecting a subset of combinations of the available modulation schemes and available levels of gain, which subset excludes the combination of any of the modulation schemes with levels of gain greater than a threshold.

15. A transmitter as claimed in claim 14 , wherein the amplification arrangement includes two amplifiers and the control system is arranged to control the amplification arrangement to provide levels of gain below the threshold by means of a first one of those amplifiers and to provide levels of gain above the threshold by means of both of those amplifiers.

16. A transmitter as claimed in claim 15 , wherein the first one of the amplifiers is implemented on a common integrated circuit with the modulator.

17. A transmitter as claimed in claim 16 , wherein the transmitter is a radio transmitter.

18. A transmitter as claimed in claim 14 , wherein the control system is responsive to a power control signal to select one of the modulation schemes and one of the levels of gain.

19. A transmitter as claimed in claim 14 , wherein the control system is configured to adopt one of the said modes under the control of a user.

20. A transmitter as claimed in claim 14 , wherein the control system is configured to, when communicating with a receiver, adopt one of the said modes under the control of the receiver.

21. A transmitter as claimed in claim 14 , wherein the control system is factory-configured to adopt one of the said modes.