Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation

Christer Andersson; David Gustafsson; Koji Yamanaka; Eigo Kuwata; Hiroshi Otsuka; Masatoshi Nakayama; Yoshihito Hirano; Iltcho Angelov; Christian Fager; Niklas Rorsman

doi:10.1109/TMTT.2012.2221140

Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
Journal article, 2012

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.

Energy efficiency

varactors

gallium nitride (GaN)

silicon–carbide (SiC)

power amplifiers

Author

Christer Andersson

GigaHertz Centre

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

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