Highly Efficient RF Transmitter Over Broad Average Power Range Using Multilevel Envelope-Tracking Power Amplifier. - Jooseung Kim; Dongsu Kim; Yunsung Cho; Daehyun Kang; Byungjoon Park; Kyunghoon Moon; Seungbeom Koo; Bumman Kim (IEEE Trans. Circuits Syst. I Regul. Pap., 2015)