Parametric hysteresis in power amplifiers

Abstract

-Parametric hysteresis in power amplifiers is investigated, studying the causes of this phenomenon and providing an efficient methodology for its prediction and elimination. As will be demonstrated, in MESFET and HEMT devices it is caused by a nonlinear resonance of the device input capacitance under near optimum input matching conditions. Bifurcation loci are used to evaluate the impact of the phenomenon under variation of critical design parameters. All the tests have been carried out in a Class-E GaN PA with measured 86.8% PAE and 12.4 W output power at 0.9 GHz.

Hysteresis and Oscillation in High-Efficiency Power Amplifiers

“…The oscillation will be extinguished either through synchronization [5,12], for input frequencies near the free-running oscillation frequency, or through inverse Hopf-type bifurcations [5][6]12]. This paper expands [3] with a detailed analysis of the oscillatory solution and the mechanisms for the oscillation extinction. Synchronization of an oscillation with an injection…”

“…LASS-E power amplifiers (PAs) have been receiving increased attention, due to their potential for simultaneously providing linear and efficient amplification when employed in bias-or load-modulation architectures [1]. However, it is not uncommon to observe instability phenomena in these amplifiers, some of which have been reported in [2][3]. Indeed, hysteresis can be found under near optimum input matching conditions, which gives rise to sudden transitions or jumps [2,[4][5] between different sections of the power-transfer curve when either increasing or decreasing the input power.…”

“…From a geometrical viewpoint, the hysteresis is due to the presence of turning points or infiniteslope points [5][6] in the solution curve, which, in designs based on commercial harmonic balance (HB), have been detected [2,4,7] with the aid of an auxiliary generator (AG). However, there is little insight into the mechanism for the appearance of these turning points, often observed when approaching the intended operation conditions [2][3].…”

“…The observation of the hysteresis phenomenon studied in detail in [3] is often empirically associated with the onset of oscillations under a relatively small variation of the circuit parameters or element values. This paper expands [3] by studying the relationship between these two phenomena, apparently quite different, which will be done through a detailed analysis of the impact of the drain bias voltage (VDS) on the turning point locus. As will be shown, the turning point locus, which at zero drain bias voltage is solely due to the input nonlinear capacitance, spreads over lower input power values.…”

Experimental Investigation of Bifurcation Behavior in Nonlinear Microwave Circuits

“…2) Example 2: HEMT power amplifier exhibiting hysteresis: The circuit of Figure 14 is a modification of a practical Lband amplifier presented in [43]. The new design uses a different output network and has been re-tuned to a fundamental frequency of 750 MHz.…”