High Efficiency and High Linearity Power Amplifiers for 5G Wireless Communication

With the increasing demand for higher data rates and the crowding of the cellular bands below 3 GHz, researchers are looking to the millimeter-wave frequency spectrum to define the next generation of mobile broadband communications. One of the biggest challenges in implementing a millimeter-wave solution is the low efficiency of commercially available millimeter-wave power amplifiers. Furthermore, the monolithic millimeter-wave integrated circuit (MMIC) power amplifiers also need to have high power with reasonable gain, good linearity and maintain a compact chip size. In Chapter 1 and Chapter 2 of this dissertation, a compact high efficiency Ka-band power amplifier and a highly linear amplifier using second harmonic injection will be demonstrated.;The requirements are even more stringent when the amplifiers are deployed in wireless systems that have high peak to average power ratio (PAPR). Among the most popular solutions to achieve high efficiency at power back-off is the Doherty architecture. Thus far, Doherty power amplifiers have been primarily implemented in the spectrum below 3 GHz for cellular base stations. Very few millimeter-wave Doherty PA's have been reported to date. The conventional Doherty architecture has several inherent drawbacks that cause low efficiency, occupy large chip size and limit the performance bandwidth. Therefore, in our work, we propose four different Doherty amplifier topologies improve the DPA performance:;1) An ultra-compact Doherty amplifier using 3-dimensional broadside coupler.;2) A wideband reconfigurable Doherty amplifier.;3) A high power density stacked-FET Doherty power amplifier with asymmetrical gate bias 4) A high efficiency asymmetrical Doherty power amplifier using novel load modulation scheme based on load-pull data.;All the proposed DPAs are fabricated in a 0.15-?m enhancement mode (E-mode) Gallium Arsenide (GaAs) process. The proposed techniques and experimental results will be discussed in Chapter 3, 4, 5 and 6.;The content of this dissertation is a compilation of 18 manuscripts, all of which I am the author or co-author. The titles, publishers and publication dates of the manuscripts are listed on page xii and xiii in this dissertation.