A Study on Highly Efficient Multimode/Multiband Power Amplifiers for Reconfigurable RF Transmitters

Abstract

Flexible and reconfigurable radio frequency (RF) transmitters with multimode and multiband capability are indispensable to handle the various evolving wireless communication systems. This thesis focuses on advanced power amplifier (PA) architectures for multimode multiband operation. Four major works toward flexible transmitters are explored in this thesis. First, a class-AB/F PAs is introduced for multimode operation. The class-F operation of the PA is highly efficient and comparable to the class-F PA. The class-AB operation is also highly efficient and linear.Second, Doherty PAs for handset applications are analyzed and implemented with the simplified circuit structure. Proper input power division and output combination assist the PA’s load modulation and result in great performance of efficiency and linearity. Third, a bandwidth (BW)-enhanced Doherty PA is proposed. The BW limiting factors are addressed and the PA utilize a lower Q of quarter-wavelength transformer and eliminates the phase compensation circuit and the additional offset line to enhance the overall BW of the Doherty PA.Finally, a multimode/multiband PAs with a boosted supply modulator is developed for handset applications. A linear broadband class-F amplifier is designed for multiband operation. The efficiency and bandwidth are enhanced by the boosted supply modulator. Multimode operation for various wireless application is accomplished thanks to programmable hysteresis control and automatic switching current adaptation from the hybrid switching amplifier. All the works are implemented for demonstration using CMOS and HBT technologies. The efforts could result in multimode multiband operation of the RF transmitter for the future intelligent radio terminals.