Power control
An amplification stage comprising: an input scaling block for scaling an input signal based on an input scaling factor to generate a scaled version of the input signal; a power amplifier for receiving the scaled version of the input signal and for generating an amplified version of said signal; an envelope detector for generating a signal representing the envelope of the input signal; an envelope scaling block for scaling the envelope signal based on an envelope scaling factor to generate a scaled version of the envelope signal; a non-linear mapping block for generating a voltage representative of the supply voltage based on the scaled envelope signal; a modulator for generating a power supply voltage for the amplifier based on the voltage generated by the non-linear mapping block; and a power control block for maintaining a linear relationship between the envelope scaling factor and the input scaling factor.
1. An amplification stage comprising:
a power amplifier for receiving a scaled version of an input signal and for generating an amplified version of said signal; and
a modulator for generating a power supply voltage for the amplifier in dependence on a scaled envelope signal, the amplification stage being configured to receive power control information, and generate an envelope scaling factor and an input scaling factor whilst maintaining a relationship between the envelope scaling factor and the input scaling factor in dependence on the received power control information.
2. The amplification stage of claim 1 wherein an envelope scaling block comprises a multiplier for multiplying the envelope signal by the envelope scaling factor.
3. The amplification stage of claim 1 wherein an input scaling block comprises a variable gain amplifier, the gain of the variable gain amplifier being controlled in dependence on the input scaling factor.
4. The amplification stage of claim 3 wherein there is further provided a mapping block for distributing the gain control information to two or more variable gain stages.
5. The amplification stage of claim 1 , wherein the envelope signal is further scaled in dependence on the difference between the voltage level at the output of a non-linear mapping block, which generates an input to the modulator in dependence on the scaled envelope signal, and the output of the modulator.
6. The amplification stage of claim 5 , further comprising:
a variable gain amplifier connected between the output of the non-linear mapping block and the input of the modulator, the gain of the variable amplifier being determined in dependence on a difference between the voltage level at the output of the non-linear mapping block and the output of the modulator.
7. The amplification stage of claim 1 , wherein the gain of an input scaling block for scaling the input signal is further determined in dependence on the difference between the voltage level at the input of power amplifier and the voltage level defined by the power control information.
8. A method in an amplification stage, comprising
scaling an input signal in dependence on an input scaling factor to generate a scaled version of the input signal;
generating an amplified version of scaled version of the input signal;
generating a signal representing the envelope of the input signal;
scaling the envelope signal in dependence on an envelope scaling factor to generate a scaled version of the envelope signal;
generating a voltage representative of the supply voltage in a non-linear mapping block in dependence on the scaled envelope signal;
generating a modulated power supply voltage for the amplifier in dependence on the voltage generated by the non-linear mapping block;
receiving power control information; and
maintaining a relationship between the envelope scaling factor and the input scaling factor in dependence on the power control information.
9. The method of claim 8 wherein further comprising multiplying the envelope signal by the envelope scaling factor.
10. The method of claim 8 further comprising controlling the gain of a variable gain amplifier in dependence on the input scaling factor.
11. The method of claim 10 further comprising distributing the gain control information to two or more variable gain stages using a mapping function.
12. The method of claim 8 , further comprising scaling the envelope signal in dependence on the difference between the voltage level at the output of the non-linear mapping block and the output of the voltage modulator.
13. The amplification stage of claim 8 , further comprising scaling the input signal further in dependence on the difference between the voltage level at the input of power amplifier and the voltage level defined by the power control information.
14. The amplification stage of claim 1 further comprising an input scaling block for scaling the input signal in dependence on the input scaling factor.
15. The amplification stage of claim 1 further including: an envelope detector for generating a signal representing an envelope of the input signal; an envelope scaling block for scaling the envelope signal in dependence on the envelope scaling factor to generate the scaled version of the input envelope signal; and a non-linear mapping block for generating a voltage representative of the supply voltage, in dependence on the scaled envelope signal, for the modulator.
16. The amplification stage of claim 1 further comprising a power control block for receiving the power control information.
17. The amplification stage of claim 1 wherein the amplification stage is further configured to maintain a substantially linear relationship between the envelope scaling factor and the input scaling factor to generate the scaled version of the input signal.
18. The method of claim 8 wherein the relationship is a substantially linear relationship.