Miniaturized Broadband Doherty Power Amplifier Using Simplified Output Matching Topology

Abstract

This paper presents a Doherty power amplifier (DPA) with reduced size and wide bandwidth by using a simplified output matching topology. In broadband DPA designs, post-matching networks are usually added after the combing node, which usually occupy large circuit sizes. However, in this design, the post-matching network is not used. Instead, two ideal transformers and specific output matching components are employed at carrier and peaking branches. Then, by rearranging the output matching components in the two branches, Norton transformation can be used and the ideal transformers can be eliminated. In this way, the impedance at the combining node is directly matched to a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> load without using a post-matching network, resulting in both compact size and wide bandwidth. For verification, a broadband DPA prototype with a very simple structure is implemented. The fabricated circuit shows a compact size. A wide bandwidth from 1.3 to 2.8 GHz (73%) is achieved with a saturated output power of 41.4–44.6 dBm. The drain efficiencies at saturation and 6-dB back-off power level are 60.1–79.1% and 41.8–61%, respectively, which are comparable to those of state-of-the-art designs.