Optimum operation of asymmetrical-cells-based linear Doherty power Amplifiers-uneven power drive and power matching

• Published in: IEEE transactions on microwave theory and techniques Vol. 53; no. 5; pp. 1802 - 1809
• Main Authors: KIM, Jangheon, CHA, Jeonghyeon, KIM, Ildu, KIM, Bumman
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adjacent channel leakage ratio (ACLR); Amplifiers; Amplitude modulation; Applied sciences; asymmetric power amplifier; Asymmetry; Carriers; Channels; Circuit properties; Circuits; Doherty amplifier; efficiency; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; High power amplifiers; Impedance; Intermodulation; linear power amplifier (LPA); Linearity; Matching; Modulation; Operational amplifiers; Phase modulation; Power amplifiers; Power generation; Power measurement; Performance evaluation; MOSFET; Output power; Input signal; Lateral diffusion; Wireless telecommunication; Linear amplification; Doherty amplifier; Implementation; Optimization; Adjacent channel leakage ratio (ACLR); Modulation; Intermodulation; Peak power; efficiency; Third order; linear power amplifier (LPA); Adjacent channel; asymmetric power amplifier; Class AB; Linearity; Code division multiple access; Power amplifier; Sinusoidal excitation; Dynamic load
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.847073

We developed a Doherty amplifier with uneven input drive and optimized individual matching for the carrier and peaking cells. In the proposed amplifier, higher input power is delivered to the peaking cell rather than the carrier cell for optimized linear power operation, especially for appropriate load modulation. Both cells are matched differently to further optimize the performance. We analyzed the efficiency of the proposed amplifier as a function of the input drive ratio for the two cells. To interpret the linearity related to the load modulation and harmonic cancellation mechanisms, we simulated the third-order intermodulation amplitude and phase of each cell of the proposed amplifier. For verification, we implemented the asymmetric power amplifier with uneven drive and optimized power matching using Motorola's MRF281SR1 LDMOSFET with a 4-W peak envelope power. For a 2.14-GHz forward-link wireless code-division multiple-access signal, the measured drain efficiency of the amplifier is 40%, and the measured average output power is 33 dBm at an adjacent channel leakage ratio (ACLR) of -35 dBc, while those of the comparable class-AB amplifier are 21% and 30.6 dBm at the same ACLR level, respectively.