Simulation and experimental results of source harmonic tuning on linearity of power GaAs FET under class AB operation

Abstract

Nonlinearity of GaAs FET amplifiers under class Ap)operation such as abrupt increase of the output power against the input power can be effectively reduced by suppressing even-order harmonic distortion in gate RF voltage. In this paper, we demonstrate the effect of the source harmonic tuning and condition for improving the linearity of power GaAs FET's under class AB operation by the source harmonic tuning technique. not driven in the optimum circuit condition under class AB operation. On improvement of efficiency in power amplifiers, a harmonic reaction microwave amplifier has been plre posed [3], and the design method and performances have been demonstrated [3], [4]. However, they have shown the optimum design parameters only for the output malching conditions, and much attention has not been paid for the conditions of the input matching circuits. On the other hand, a sourcx hairmonic controlled circuit has been proposed [5], and it has shown the harmonic tuning effect on the efficiency under class F or B operation; however, the linearity of a class AB amplifier has not been tiis-

Theoretical facet and experimental results of harmonic tuned PAs

“…(19), output harmonic tuning results in an improvement of the drain efficiency; otherwise, if I 1 and I 2 are in phase, the best solution is to short circuit the I 2 component and to terminate I 1 on its optimum resistive load (TL approach), that is, V DD Ϫ V k )/I 1 in order to avoid ␦ 2HM Ͻ 1 and lowering the drain efficiency [21,22].…”

Multiharmonic manipulation for highly efficient microwave power amplifiers

“…If reasonable drive levels are considered, the control voltage V gs exhibits a major second harmonic content, leading to an asymmetrical gate-source voltage waveform, as depicted in Figure 12. To avoid this effect, which is often considered as detrimental, the input harmonic terminations are frequently set to short-circuit values [15,17] or compensated by means of a counteracting nonlinearity [16]. Nevertheless, major improvements of power performances are obtained if such a second harmonic input voltage component is used to implement the technique described beforehand.…”

“…On the other hand, other aspects like the influence of input harmonic terminations different from the normally used short-circuiting solution have to be considered. As an example, the second harmonic terminating control schemes, both at input and output ports, are fruitfully employed [15][16][17][18][19][20] or particular driving waveforms have been suggested [21]. Unfortunately, in open literature, such second harmonic approaches (mainly experimental and with a lack of physical insight) often resulted in confusing contributions, reporting even contradictory results and conclusions.…”

Nonlinear approaches to the design of microwave power amplifiers

“…The influence of input harmonic terminations has to be considered, thus leading to a selection that may differ from the normally adopted short-circuiting solution. As an example, 2-harmonic terminating control schemes, at both input and output ports, has been demonstrated to be effective only if correctly implemented [21][22][23]. In the open literature however, such 2 nd -harmonic approaches have resulted in confusing contributions, leading to conflicting results and conclusions [24,25].…”