Output harmonic optimisation of dynamically load modulated power amplifiers

Load Modulation of Harmonically Tuned Amplifiers and Application to Outphasing Systems

“…For the load modulation trajectory to maintain the same mode of operation (and with the same value of δ) throughout the back-off region, both fundamental and second harmonic impedance load modulation is theoretically required [39], [41], [42]. In [39] it was noted that by moving across the design space with a fixed second harmonic termination, it is possible to determine in closed form a fundamental optimal load modulation trajectory with waveforms still maintaining the same B/J relationship.…”

“…The closed form equations for the optimal load modulation trajectories for continuous mode B/J are compared to loadpull characterisation measurements on a 25W GaN Highelectron-mobility transistor (HEMT) device manufactured by Wolfspeed (CGH40025) previously presented in [42]. The measurements are carried out using Toshiba's Research Development Centre's passive harmonic load/source-pull measurement system in Kawasaki, Japan.…”

“…Continuous modes of operation theory has also been exploited for dynamic load modulated (DLM) [40] and Doherty systems [1], [2]. When applied to load modulated systems, it has been shown in our previous work [39], [41], [42] that it can be beneficial to use Harmonically Tuned (HT) amplifier modes in DLM and outphasing systems, as it is possible to move across the continuous design space, when complex load modulation is applied. Particularly, the complex fundamental optimal load trajectory of HT amplifiers makes them wellsuited to outphasing systems, in which a complex loading is inherently presented to the branch PAs -even if reactance compensation techniques are implemented [39].…”

A Study on Highly Efficient Dual-Input Power Amplifiers for Large PAPR Signals

“…Although single-input power amplifiers are inherently plug-and-play like and hence easily upgradable, to enable alternative methods of efficiency enhancement, multiple-input power amplifiers have become more popular in recent years. Multiple-input power amplifiers include envelope tracking (ET) [14]/envelope elimination and restoration(EER) [15] power amplifiers (PAs), dynamic load modulation (DLM) PAs [16][17][18], dual-input Doherty amplifiers [19] and outphasing amplifiers [20][21][22][23][24]. ET/EER PAs, which improve the efficiency by modulating the supply voltage, require an envelope modulator, which is a complex circuit to modulate the power supply.…”