An Ultra-Broadband GaN Doherty Amplifier with 83% of Fractional Bandwidth

This letter presents the design and characterization of an ultra-broadband GaN Doherty amplifier with more than an octave bandwidth. The developed architecture is based on ultra-wideband input/output splitting/combining networks capable to mitigate the typical frequency limiting factors of the traditional Doherty amplifier. The innovative design approach is demonstrated through a practical prototype realization based on commercial GaN-HEMT devices. From 1.05 to 2.55 GHz, continuous wave measurements have shown efficiency levels within 58% and 35% at 6 dB of output power back-off and within 83% and 45% at saturation, with an output power around 41 dBm. The performance of the prototype have also been evaluated by applying WiMAX and 3GPP modulated signals at different carrier frequencies, showing promising results.