Techniques for Power Dynamic Range and Back-Off Efficiency Improvement in CMOS Digitally Controlled Polar Transmitters

Techniques to extend the power dynamic range and to reduce the dc power consumption in back-off for a multiband CMOS digitally controlled polar transmitter are described. The techniques are applied to a transmitter comprising a digitally controlled buck converter and a current-mode class-D RF amplifier with digitally controlled unit cells. The power dynamic range is improved by using tri-state unit-cells (rather than the customary “on-off” controlled cells) to reduce the feed-through power. The measured overall power dynamic ranges are 91 and 85 dB, at 0.85 and 1.75 GHz, respectively. DC power consumption at low power was reduced by introducing a new charge-sampling mode of operation for the buck converter in addition to the customary pulse-width modulation operation. Experimental results showed dc power consumption reduced by 30% at low power.