Power Control of a Switching Amplifier for GSM Handsets
Sprache des Titels:
Proc. 2002 APMC
Maximizing the efficiency of GSM handset power amplifiers (PA) for a significant increase of talk-time is the main aim in new design approaches. One of them is the utilization of switching amplifiers, since they offer extremely high efficiency and their disadvantages are not applicable to constant-envelope modulation schemes like GMSK used in the GSM system. Among them, the Class-E amplifier concept is best suited, because it allows about 80% efficiency, while maintaining an excellent output spectrum and reasonable gain. Since the power transistor operates as a switch, the input signal envelope is not reproduced accordingly at the output. In this paper, four ways of output power control are presented and compared: Variable supply voltage by utilizing a DC/DC converter, a serial transistor and PA mixed mode operation by reducing the gate voltage swing as well as variation of the duty cycle.