Multioctave Power Amplifier Design Using 9:1 Planar Impedance Transformer

In this letter, at the first step, design of a new broadband planar 9:1 transmission line impedance transformer is investigated and several parameters of this transformer, such as characteristic impedances of the lines, their length, and ground plane distance effects, are analyzed from a new point of view. Then, a multioctave power amplifier (PA) is implemented using the introduced transformer as input and output matching network of a power transistor. The fabricated PA achieves a power output more than 46.5 dBm with a flat gain of 10.5 ± 0.7 dB over an ultrawide frequency band from 0.5 to 3 GHz. The measured power added efficiency (PAE) is better than 50% over the whole frequency bandwidth.