L-band AlGaN/GaN power amplifier with protection against load mismatch

Solid-state power amplifiers need protection at the output to handle high reflections due to mismatch. Normally this is implemented by using a ferrite-based isolator. These are however large and bulky components. This paper presents a Gallium-Nitride power amplifier module with automatic protection against large reflections based on fold-back protection, by sensing the reflected power. Measurements have been performed on a 100 W L-band power amplifier module at full reflection (short at the output) without damage to the amplifier. The reaction time of the protection mechanism is less than 0.5 μs.