Increased Efficiency of a Current Compensating Load Modulation Based MMIC Doherty Power Amplifier Design In 0.25m GaAs pHEMT Technology

Abstract

In this work, a premise is applied to the conventional load modulation equation of Doherty power amplifier (DPA) in 0.25 m GaAs pHEMT technology to compensate output impedance of main amplifier ( Z out,main ) variation, even in low power region. Using this modified modulation leads to the DPAs power added efficiency (PAE) increase in comparison by the case in which the load modulation revision is ignored, which is also designed in this paper. Second harmonic rejection networks are also added to both designs to play their roles as to efficiency increase. By doing so, the revised load modulation based DPA has the maximum PAE of 39.6%, maximum output power ( P out ) of 31.61dBm, at 8 GHz. Simulation results of this DPA in higher harmonics indicate the designed DPA has the minimum second and third harmonics power of -51.7 dBm and -80 dBm, respectively. For the sake of linearity evaluation, it is depicted that 1dB-power gain compression has not occurred in the input power (P in ) range in which the proposed DPA works.

Extended Bandwidth and Increased Efficiency Quasi-Doherty Power Amplifier Design With A Revised Approach For Load Modulation

“…However, this approach has its own disadvantages: bandwidth degradation due to narrowband behavior of 4  TL, not expecting Zout,main variation with power in which such changes are needed to be applied in a revised load modulation [23], to name but a handful. Load modulation begins when PAaux commences power amplification.…”

“…By studying the field of designing PAs, in retrospect, it can be understood several different PA design methods are introduced to increase PAs' PAE, bandwidth, to name but a handful. Such methods comprise envelope tracking [1][2][3][4][5], switching mode class PAs [6][7][8][9][10], harmonically tuned class PAs [10][11][12][13][14][15], Cherix outphasing [16][17][18][19][20], and DPA [21][22][23][24][25]. DPA is one such PA that is still under more scrutiny to subdue the related restrictions of exerted technology and try to reach the best possible performance of that PA [26][27][28][29][30].…”

“…According to [23], revising load modulation can be done based on linear modeling of the variations in Zout,main's trajectory in power sweep at modulation equation. This load modulation modification led to the PAE increase in comparison by the condition in which a conventional modulation was applied to DPA.…”