Issues on the design of a variable power LINC amplifier system in SiGe operating at 2.4 GHz

An increasing number of wireless communicationsystems require linear transmitters that can achieve highefficiency. Good linearity is necessary for bandwidth efficientmodulation while poor efficiency directly affects operationalcosts and causes thermal losses in the base station. This paperexamines the implementation of the outphasing technique, alsoknown as Linear Amplification with Nonlinear Components(LINC) using a 0.25 ?m SiGe BICMOS process. Adaptation ofthe amplifier in order to achieve different power levels, via theuse of Class-F amplifying sections working in parallel is alsoexamined. The effects of the input and output mismatchintroduced when changing the power level are discussed andpossible solutions presented. Furthermore, specific problemswhich arise when using a bipolar technology are addressed. Thiswork also discusses the adaptation of a tunable phase shifter fora 1 V supply and wide-linear range. The 2.4 GHz amplifiersystem presented in this work achieved a 3-level power controlwith a maximum PAE in the range of 58-73%