Multi-Octave bandwidth, 100 W GaN power amplifier using planar transmission line transformer

In this paper, design, implementation, and experimental results of efficient, high-power, and multi-octave gallium nitride-high electron mobility transistor power amplifier are presented. To overcome the low optima source/load impedances of a large transistor, various topologies of a broadside-coupled impedance transformer are simulated, implemented, and measured. The used transformer has a flat measured insertion loss of 0.5 dB and a return loss higher than 10 dB over a decade bandwidth (0.4-4 GHz). The transformer is integrated at the drain and gate sides of the transistor using pre-matching networks to transform the complex optima source/load impedances to the appropriate impedances of the transformer plane. The measurement results illustrate a saturated output power ranged between 80 and 115 W with an average drain efficiency of 57% and gain of 10.5 dB across 0.6-2.6 GHz.