A 39 GHz Doherty-Like Power Amplifier With 22dBm Output Power and 21% Power-Added Efficiency at 6dB Power Back-Off

Abstract

The design of a Doherty-like power amplifier for millimetre-wave (mm-wave) applications is presented in this work. The designed power amplifier employs a novel symmetrical load-modulated balanced amplifier (S-LMBA) architecture. This design is advantageous in minimizing the undesired impedance interaction often encountered in the classic LMBA approach. Such interactions are typically due to the use of a non- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> load at the isolation port of the output quadrature coupler. Moreover, magnitude and phase control networks are carefully designed to generate the specific magnitude and phase information for the designed S-LMBA. To demonstrate the proposed ideas, the S-LMBA is fabricated in a 45-nm CMOS SOI technology. At 39 GHz, a 22.1 dBm saturated output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{\mathrm {sat}}$ </tex-math></inline-formula> ) with a maximum power-added efficiency (PAE) of 25.7% is achieved. In addition, 1.68 times drain efficiency enhancement is obtained over an ideal Class-B operation, when the designed S-LMBA is operated at 6 dB power back-off. An average output power of 13.1 dBm with a PAE of 14.4% at an error vector magnitude (EVM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {rms}}$ </tex-math></inline-formula> ) above -22.5 dB and adjacent channel power ratio (ACPR) of -23 dBc is also achieved, when a 200 MHz single carrier 64-quadrature-amplitude-modulation (QAM) signal is used. Including all testing pads, the footprint of the designed S-LMBA is only 1.56 mm2.

Topics & Concepts