High-Efficiency Class-E-Cells-Based GaN HEMT Doherty Amplifier for WCDMA Applications

This paper represents a high-efficiency GaN high electron mobility transistor (HEMT) class-E Doherty amplifier (CEDA) for wide-band code division multiple access (WCDMA) applications. The class-E power amplifiers (PAs) with significant harmonic suppression are used as the carrier and peaking cells. To further improve the efficiency, the asymmetrical drain biases are applied to the CEDA. For validations, the class-E PA is designed and implemented with 25-W GaN HEMT at 2.14 GHz. From the measured results for a single tone, the peak power-added efficiency (PAE) and drain efficiency of 73.5% and 76.5% are achieved with a gain of 14.1 dB at an output power of 43.1 dBm by suppressing harmonic power levels below -60 dBc. For the proposed CEDA, the PAE and drain efficiency of 56.1% and 61.2% is achieved at 40 dBm (6-dB back-off power from Psat) for a single tone. For a 1-carrier WCDMA signal, the PAE of 57.2% is obtained with an adjacent channel leakage ratio (ACLR) of -27.2 dBc at 40 dBm, which is 9.6% improvement over the conventional Doherty amplifier with an ACLR of -29.5 dBc.