RF power amplifiers using magnetically coupled line transformers

Abstract

The power amplifier has been one of the crucial components in wireless communication systems. Particularly, for mobile handsets, the power amplifier is the most power consuming block and seriously affects the talk-time of the handsets. Therefore, to reduce the output matching loss, the power amplifiers need high Q passive components, which are hard to be realized using MMIC technology. Usually, the output matching networks are implemented with high Q microstrip lines on dielectric substrates and surface-mount type (SMT) capacitors. The current power amplifier modules are composed of a GaAs HBT power amplifier, microstrip lines, and SMT capacitors. The power amplifier modules are bulky and expensive with the additional passive components. The future power amplifier module would adopt a cheap standard package, and the MMIC power amplifier would include all matching components on GaAs or Si substrates. The future power amplifier module will be composed of a MMIC power amplifier with on-chip input/output networks, bond wires, and a standard package. Undoubtedly, the power amplifier module is small and cheap because of no additional passive components. This thesis presents CMOS and HBT power amplifiers using on-chip magnetically coupled lines for low loss output matching networks. For the integrated output network, various coupled lines were characterized and compared. For balun operation, the edge-coupled lines are advantageous. The proposed autotransformer using the broadside-coupled lines shows 1:9 impedance transformation and low insertion loss. A differential class-E amplifier was analyzed with some equations. The output power is proportional to the square of the transformer’s coupling coefficient, and the efficiency is independent of the coupling coefficient. The design equations of the differential class-E amplifier were presented. A variation of class-E amplifier using an autotransformer was proposed. As the transceiver architecture is reformed and...