Wideband Sequential Circulator Load Modulated Amplifier with Back-Off Efficiency Enhancement

This paper demonstrates a novel power amplifier (PA) architecture; the sequential circulator load modulated amplifier (SCLMA). The sequential configuration resulted in excellent bandwidth and extended back-off efficiency enhancement, making it suitable for modern communication scenarios with large peak-to-average-power-ratio (PAPR) signals. A wideband prototype PA based on GaN transistors and a commercial off-the-shelf circulator is employed to validate the SCLMA concept. The experimental results exhibit a drain efficiency of 55–68 % at the peak output power and 46–53 % at 8-dB output power back-off across 2.0-3.0 GHz. Combined with the measured peak output power of 42.7±0.7 dBm in the same range, make it a promising candidate for use in modern energy-efficient wireless communication transmitters.