A 25-to-34-GHz Doherty Power Amplifier With Reconfigurable Output Network

In this letter, a frequency reconfigurable Doherty power amplifier (DPA) is proposed. To ensure that the output-stage transistors are loaded with proper impedances over a wide bandwidth during load modulation, an output network with a compact switchable stub is designed with three operating states for three subbands. The switchable stub also adjusts the phase of the output network of the auxiliary amplifier for large output impedance under the power back-off (PBO) state. The developed DPA chip takes the size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.05\times 1.5$</tex-math> </inline-formula> mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, which achieves the small signal gain of 19.5–21.7 dB and the saturation output power of 26.3–27.8 dBm over 25–34 GHz. The measured power added efficiency (PAE) is 34%–41% at saturation and 23%–31.3% at 6-dB PBO.