A GaN MMIC Load-Modulated Balanced Amplifier With Modified Output Coupler for Efficiency Enhancement Over a Larger Power Back-Off Range

Abstract

This brief firstly presents a monolithically microwave integrated circuit (MMIC) load-modulated balanced amplifier (LMBA) developed in 0.15um GaN process. In this brief, the asymmetric output coupler is applied for further enhancing output power and output back-off (OBO) efficiency over a larger OBO range. This MMIC LMBA operating mode is dependent on a three-ways active load modulation process by modified the coupling coefficient of output coupler which can provide more design parameters and freedom. To validate the proposed LMBA at millimeter wave (mm-wave), a 24.7-25.7 GHz MMIC LMBA is demonstrated, fabricated and tested. Measurements show that this MMIC LMBA can deliver a 35.2-dBm saturated output power with a peak drain efficiency of 37.7%. At 6-dB/8-dB/10-dB OBO, 23.8-30 %, 24.2-27 % and 20-24% power added efficiencies (PAE) can be obtained, respectively. The measured S21 is 15-dB with a 1 0.4-dB gain variation. When driven by a 100MHz 64-QAM OFDM modulation signal with a PAPR of 9.2-dB, the measured ACPR is improved to -45.04 dBc with DPD. In this case, the PA achieves an average efficiency of 25.2% and a 26.2-dBm average output power.