Title :
Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
Author :
Andersson, Christer M. ; Gustafsson, David ; Yamanaka, Koji ; Kuwata, Eigo ; Otsuka, Hiroshi ; Nakayama, Masatoshi ; Hirano, Yoshihito ; Angelov, Iltcho ; Fager, Christian ; Rorsman, Niklas
Author_Institution :
Microwave Electron. Lab., Chalmers Univ. of Technol., Goteborg, Sweden
Abstract :
A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>;70%) over a large output power dynamic range (>;10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load-pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
Keywords :
microwave amplifiers; power amplifiers; silicon compounds; transistor circuits; varactors; DLM networks; SiC; SiC varactor technology; class-J microwave amplifier; class-J power amplifiers; dynamic load modulation; load impedance; multiharmonic load-pull measurements; transistor load reactance; transistor power utilization; tunable varactor technologies; Harmonic analysis; Impedance; Power amplifiers; Power generation; Resistance; Transistors; Varactors; Energy efficiency; gallium nitride (GaN); power amplifiers; silicon–carbide (SiC); varactors;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
DOI :
10.1109/TMTT.2012.2221140
