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The continuous inverse class-F mode with resistive second-harmonic impedance

: Carrubba, V.; Akmal, M.; Quay, R.; Lees, J.; Benedikt, J.; Cripps, S.C.; Tasker, P.J.


IEEE transactions on microwave theory and techniques 60 (2012), No.6, Pt.2, pp.1928-1936
ISSN: 0018-9480
Journal Article
Fraunhofer IAF ()
broadband amplifier; microwave device; microwave measurement; power amplifiers (PAs); radio frequency (RF)

In this paper, an extended version of the continuous class-F-1 mode power amplifier (PA) design approach is presented. A new formulation describing the current waveform in terms of just two additional parameters, while maintaining a constant half-wave rectified sinusoidal voltage waveform, allows multiple solutions of fundamental and second-harmonic impedances that provide optimum performance to be computed. By varying only the imaginary parts of fundamental and second-harmonic impedances, it is shown that output performance in terms of power and efficiency is maintained constant and equal to that achievable from the standard class-F-1. Indeed, when presenting resistive second-harmonic impedances, it will be demonstrated that the fundamental load can be adjusted to maintain satisfactory output performances greater than a certain predetermined target value. The measurements, conducted on a GaAs pHEMT device at 1 GHz, show a good agreement with the theoretical analysis, revealing drain efficiencies greater than 70% for a very large range of load solutions, which can translate to an ability to accommodate reactive impedance variations with frequency when designing broadband PAs.