| This dissertation proposes a ripple based variable frequency control scheme for a high bandwidth power converter. The converter is for wireless communication applications. The goal is to provide a buck converter design solution for the system application, to improve efficiency and linearity simultaneously. To enhance linearity, the theoretical derivation of switching ripple cancellation in frequency domain is given and modeled. The simulation results match the Cadence simulation and the experimental results. From the envelope tracking point of view, to support FCC power emission mask, a high-speed synchronized buck with switching ripple cancellation technique for the envelope tracking transmitter architecture is designed, measured and thoroughly derived. Detailed large and small signals analyses of the modulator design are carried out to study the effects of the parameters and to prove the system stability and high control bandwidth. The derivation results are modeled to the control theory and measurement results; they do match. A preliminary analysis of Device Segmentation strategy is also proposed for HFWB buck converter to enhance the efficiency over a wide load range. A monolithic HFWB buck converter is fabricated using the AMI 05 CMOS process. The test results show that output ripple has a significant decrease from 1.2V to 200 mV; the spectrum is spread out over a wide frequency band. |
