Method and apparatus for optimizing transmitter power efficiency
A transmitter for a mobile device utilizes at least one mapper in order to improve power efficiency while still meeting out of band spurious emissions and waveform quality requirements. An encoder and modulator generates an encoded and modulated transmit signal from an input signal. A digital to analog converter coupled to the encoder and modulator generates an analog representation of the encoded and modulated transmit signal. An amplifier stage coupled to the digital to analog converter amplifies the analog representation of the encoded and modulated transmit signal to generate a transmission signal. The transmitter further comprises an amplifier control block configured to generate an amplifier control signal for adjusting at least one parameter of the amplifier stage. At least one mapper is provided in the amplifier control block, used to determine the amplifier control signal based on a peak to average power ratio and an average transmit power of the transmission signal. Environmental and operating conditions of the transmitter may be accounted for as well in the mappers.
1. A transmitter for a mobile device, comprising:
an encoder and modulator for generating an encoded and modulated transmit signal based on an input signal;
a digital to analog converter coupled to the encoder and modulator, for generating an analog representation of the encoded and modulated transmit signal;
an amplifier stage coupled to the digital to analog converter, for amplifying the analog representation of the encoded and modulated transmit signal to generate a transmission signal; and
an amplifier control block configured to generate an amplifier control signal for adjusting at least one parameter of the amplifier stage, the amplifier control block comprising at least one mapper to determine the amplifier control signal based on a peak to average power ratio and an average transmit power of the transmission signal.
2. The transmitter of claim 1 , wherein the amplifier control block comprises:
a first mapper for generating a first signal representative of the peak to average power ratio based on a type of the encoded and modulated transmit signal;
a second mapper for generating a second signal representative of the average transmit power of the transmission signal; and
a summer for generating the amplifier control signal based on the first and second signals.
3. The transmitter of claim 1 , wherein the amplifier control block comprises a mapper configured to generate, for each of a plurality of different peak to average power ratios, a corresponding amplifier control signal based on the average transmit power of the transmission signal.
4. The transmitter of claim 3 , wherein the mapper is configured to generate the corresponding amplifier control signal further based on one or more environmental conditions in which the transmitter is operating.
5. The transmitter of claim 3 , wherein the mapper is configured to generate the corresponding amplifier control signal further based on one or more operating conditions of the transmitter.
6. The transmitter of claim 5 , wherein the operating conditions of the transmitter comprise transmit frequency and drive band.
7. The transmitter of claim 1 , wherein the amplifier stage comprises:
an automatic gain control amplifier coupled to an output of the digital to analog converter; and
a power amplifier coupled to an output of the automatic gain control amplifier, wherein the amplifier control signal adjusts at least one parameter of the power amplifier.
8. The transmitter of claim 7 , further comprising a gain control block configured to generate an automatic gain control signal for controlling gain in the automatic gain control amplifier based on an average transmit power indicator corresponding to the average transmit power of the transmission signal.
9. The transmitter of claim 8 , further comprising a gain control compensation block coupled with the gain control block in a feedback loop, wherein the gain control compensation block is configured to generate a gain correction factor for the gain control block based on the amplifier control signal.
10. The transmitter of claim 9 , wherein the gain correction factor is one of applied to the average transmit power indicator provided to the gain controller to adjust the automatic gain control signal and applied to the automatic gain control signal directly.
11. The transmitter of claim 9 , wherein the gain correction factor is an input to the gain control block, and the gain control block is configured to generate the automatic gain control signal based further on the gain correction factor.
12. The transmitter of claim 7 , wherein the at least one parameter of the power amplifier comprises at least one of a bias, a current bias, a supply voltage, a stage switch-in, a stage switch-out, a turning on, a turning off, a gain, a gain distribution, a conducting angle, an amplifier class change, a load, or an impedance.
13. The transmitter of claim 1 , wherein the amplifier control block comprises a plurality of mappers for determining a corresponding plurality of amplifier control signals based on the peak to average power ratio and the average transmit power of the transmission signal.
14. The transmitter of claim 13 , wherein at least one of the plurality of amplifier control signal adjusts a supply voltage or current bias of the amplifier stage.
15. The transmitter of claim 1 , wherein the amplifier control signal and the analog representation of the encoded and modulated transmit signal are delay aligned.
16. The transmitter of claim 1 , wherein the amplifier control signal is advanced in time with respect to the analog representation of the encoded and modulated transmit signal.
17. The transmitter of claim 1 , wherein the analog representation of the encoded and modulated transmit signal is delayed in time with respect to the amplifier control signal.
18. The transmitter of claim 1 , wherein at least one of the encoder and modulator, digital to analog converter, and amplifier stage generates a stepped response; and wherein the at least one mapper comprises a plurality of stored arrays or look up tables; and further wherein one of the plurality of stored arrays or lookup tables is selected based on an input to the at least one of the encoder and modulator, digital to analog converter, and amplifier stage and the stepped response.
19. A mobile device comprising:
a processor for controlling the operation of the mobile device;
a memory coupled to the processor; and
a transmitter for generating a transmission signal, the transmitter comprising:
an encoder and modulator for generating an encoded and modulated transmit signal based on an input signal;
a digital to analog converter coupled to the encoder and modulator, for generating an analog representation of the encoded and modulated transmit signal;
an amplifier stage coupled to the digital to analog converter, for amplifying the analog representation of the encoded and modulated transmit signal to generate the transmission signal; and
an amplifier control block configured to generate an amplifier control signal for adjusting at least one parameter of the amplifier stage, the amplifier control block comprising at least one mapper to determine the amplifier control signal based on a peak to average power ratio and an average transmit power of the transmission signal.
20. A method of optimizing power efficiency in an amplifier stage, the method comprising:
generating an encoded and modulated transmit signal based on an input signal;
generating an analog representation of the encoded and modulated transmit signal;
amplifying the analog representation of the encoded and modulated transmit signal in the amplifier stage to generate a transmission signal;
generating an amplifier control signal based on a peak to average power ratio and an average transmit power of the transmission signal; and
adjusting at least one parameter of the amplifier stage using the amplifier control signal.
21. A non-transitory computer-readable storage medium storing instructions executable by a processor coupled to the storage medium, the instructions, when executed by the processor, cause the processor to perform acts of a method of optimizing power efficiency in an amplifier stage, said acts comprising:
generating an encoded and modulated transmit signal based on an input signal;
providing the encoded and modulated transmit signal to a digital to analog converter to generate an analog representation of the encoded and modulated transmit signal, wherein the analog representation of the encoded and modulated transmit signal is amplified in the amplifier stage to generate a transmission signal;
generating an amplifier control signal based on a peak to average power ratio and an average transmit power of the transmission signal; and
adjusting at least one parameter of the amplifier stage using the amplifier control signal.
22. A control system for a mobile device transmitter, the mobile device transmitter comprising an amplifier stage for generating a transmission signal, the control system comprising:
an input terminal for receiving a signal representative of an average transmit power of the transmission signal;
at least one mapper for determining an amplifier control signal based on the average transmit power and a peak to average power ratio of the transmission signal; and
an output terminal for providing the amplifier control signal to the amplifier stage for adjusting at least one parameter of the amplifier stage.
23. A method of operating an amplifier stage of a mobile device transmitter for generating a transmission signal, the method comprising:
receiving a signal representative of an average transmit power of the transmission signal;
determining an amplifier control signal by mapping the average transmit power and a peak to average power ratio of the transmission signal to a control value for the amplifier stage; and
providing the amplifier control signal to the amplifier stage for adjusting at least one parameter of the amplifier stage according to the control value.
24. A non-transitory computer-readable storage medium storing instructions executable by a processor coupled to the storage medium, the instructions, when executed by the processor, cause the processor to perform acts of a method of operating an amplifier stage of a mobile device transmitter for generating a transmission signal, said acts comprising:
receiving a signal representative of an average transmit power of the transmission signal;
determining an amplifier control signal by mapping the average transmit power and a peak to average power ratio of the transmission signal to a control value for the amplifier stage; and
providing the amplifier control signal to the amplifier stage for adjusting at least one parameter of the amplifier stage according to the control value.