High-efficient class F GaAs FET amplifiers operating with very low bias voltages for use in mobile telephones at 1.75 GHz

Theoretical facet and experimental results of harmonic tuned PAs

“…On the other hand, some improvements on the efficiency can be achieved by properly choosing the harmonic voltage ratios, as was demonstrated in the high-frequency Class F approach [14]. In fact, in this case, assuming the 3 rd to 1 st harmonic voltage ratio (k 3 in this article) is higher (namely, k 3 ϭ Ϫ1/6) than in the ideal squared voltage waveform (corresponding to k 3 ϭ Ϫ1/3), a slight improvement on the drain efficiency was achieved.…”

“…If more realistic assumptions are adopted, accounting also for the actual phase relationships between voltage and current harmonic components, both Class C and deep Class AB (near B) operating conditions lead to poor efficiency performances [13]. Nevertheless, the Class F strategy, for instance, has been successfully applied in Class AB [14,15].…”

Study on Large-signal Linearity and Efficiency of AlGaN/GaN MODFETs

“…However, an improvement of ~ 12 % on PAE with harmonic frequency terminations was found at high input power levels. Harmonic tuning allows improvement of device efficiency by changing the load line of devices [3]. Since the load line was found to be less steep when the output power is terminated properly at harmonic frequencies, the PAE increases correspondingly.…”

High‐efficiency class‐F power amplifier with broadband performance

“…(1) are used to initialize the amplitude and phase values of the output voltage generators. The load-cycle is then tuned in order to achieve the required trade-off between output power and efficiency [5], and the input and output impedances to be presented to the transistor at the fundamental and harmonic frequencies are derived.…”

“…Photonic bandgap (PBG) structures, which have periodic arrays of etched on the ground plane, have been investigated to produce a wide stopband in frequency ranges that include the microwave-frequency band by properly-scaled dimensions. However, PBG structures are more difficult to design for the passive or active circuits in microwave and millimeter devices, since in finding the PBG structure's equivalent circuit is difficult due to too many design parameters, such as cell numbers, cell size, cell distance, and filling factor [3][4][5]. Recently, defect ground structures (DGS) with periodic or nonperiodic structures etching off a defected pattern from the ground plane have provided a wide rejection band in some frequency ranges [5][6][7].…”