Wireless communication unit and power control system thereof
View Patent ↗A wireless communication unit comprises a transmitter having an analogue feedback power control loop having a power control function arranged to set an output power level of the transmitter. The power control function comprises a predictor sub-system arranged to reduce sensitivity to loop latency of the analogue feedback power control loop. The use of a predictor sub-system provides reduced sensitivity to loop latency, gain variations and delay.
1. A wireless communication unit comprises:
a transmitter comprising an analogue feedback power control loop having a power control function arranged to set an output power level of the transmitter, the power control function comprising a predictor sub-system arranged to reduce sensitivity to loop latency of the analogue feedback power control loop, the predictor sub-system comprising a digital control system having a digital inner feedback loop that is to be closed based upon a predicted power control level, the digital inner feedback loop comprising:
a first summing junction;
a predictor; and
a gain stage.
2. A wireless communication unit according to claim 1 wherein the predictor sub-system is arranged to support transmission in an 8-PSK mode and a GMSK mode of operation.
3. A wireless communication unit according to claim 1 wherein the digital control system further comprises a digital outer feedback loop that is to be closed based upon a modeling or predictor error in GMSK mode.
4. A wireless communication unit according to claim 3 wherein the digital outer feedback loop comprises:
a second summing junction;
the first digital inner feedback loop;
a digital delay; and
a third summing junction that is to be closed based upon a modeling or predictor error.
5. A wireless communication unit according to claim 1 wherein the analogue feedback power control loop comprises a coupler and a log-detector providing a wide power control range.
6. A wireless communication unit according to claim 5 wherein the analogue feedback power control loop comprises a digital-to-analogue converter (DAC) wherein an offset voltage associated with the DAC, is arranged to be lower than an offset-voltage of the log detector.
7. A wireless communication unit according to claim 1 wherein the analogue feedback power control loop is arranged to be a low-latency, high-gain analogue loop.
8. A wireless communication unit according to claim 1 wherein the digital control system comprises a ramp generation circuit having a linear translator arranged to autoscale a ramp reference.
9. A wireless communication unit according to claim 8 wherein the linear translator is operably coupled to a log predistortion arranged to counteract an effect of the log detector.
10. A wireless communication unit according to claim 9 wherein the linear translator outputs a low-power multiplier signal to autoscale a reference in GMSK mode.
11. A wireless communication unit according to claim 8 wherein the linear translator outputs an amplitude modulated signal to autoscale a reference in 8-PSK mode.
12. A wireless communication unit according to claim 11 wherein a control slope of a ramp-down signal of the transmitter is switched to unity when ramping down.
13. A wireless communication unit according to claim 1 wherein the gain stage is set to zero to support a bypass mode.
14. A wireless communication unit according to claim 1 wherein the digital control system predictor subsystem combines a linear phase or constant group delay of a system to be combined with pure latency or delay of a system.
15. A wireless communication unit according to claim 1 wherein the digital control system comprises a saturation detection plus correction system.
16. A wireless communication unit according to claim 1 wherein the digital control system comprises an activity detector in GMSK mode.
17. A wireless communication unit according to claim 16 wherein a digital controller of the digital control system sets a signal amplitude reference for the analogue feedback power control loop.
18. A wireless communication unit according to claim 1 wherein the digital control system comprises a step attenuator controller in 8-PSK mode.
19. A wireless communication unit according to claim 1 wherein the transmitter supports a low power mode, whereby components in the analogue feedback loop are disabled when targeting a low power amplifier output power.
20. An integrated circuit for use in a wireless communication device comprises:
a transmitter;
an analogue feedback power control loop having a power control function arranged to set an output power level of the transmitter; and
wherein the power controller comprises a predictor sub-system arranged to reduce sensitivity to loop latency of the analogue feedback power control loop, the predictor sub-system comprising a digital control system comprising:
a digital inner feedback loop that is to be closed based upon an estimated or predicted power control level; and
a ramp generation circuit having a linear translator arranged to autoscale a ramp reference.
21. An integrated circuit according to claim 20 wherein the linear translator is operably coupled to a log predistortion arranged to counteract an effect of the log detector.
22. An integrated circuit according to claim 20 wherein the linear translator outputs an amplitude modulated signal to autoscale a reference in 8-PSK mode.
23. A wireless communication unit comprises:
a transmitter;
an analogue feedback power control loop having a power control function arranged to set an output power level of the transmitter; and
wherein the power controller comprises a predictor sub-system arranged to reduce sensitivity to loop latency of the analogue feedback power control loop, the predictor sub-system comprising a digital control system comprising:
a digital inner feedback loop that is to be closed based upon an estimated or predicted power control level; and
a ramp generation circuit having a linear translator arranged to autoscale a ramp reference.
24. A wireless communication unit according to claim 23 wherein the predictor sub-system is arranged to support transmission in an 8-PSK mode and a GMSK mode of operation.