Design of a current mode class-D RF amplifier using load pull techniques

This work presents the design of a current mode class-D (CMCD) amplifier using a measurement based approach. Because the CMCD amplifier is in fact a push-pull version of the inverted class-F amplifier the optimum load impedances for an inverted class-F single-ended operated LDMOS FETs have been determined using an active harmonic load-pull setup. The correct time domain waveforms for an inverted class-F amplifier were verified by measurements and simulations. Based on the harmonic load-pull measurements an experimental current mode class-D amplifier with 61.5% power-added efficiency (PAE) at 25W output is demonstrated using LDMOS FETs at 900 MHz.

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