Phase Compensated Sequential Load Modulated Balanced Amplifier Using Harmonically Tuned Control Amplifier

This paper presents a new solution for phase compensation in the sequential load modulated balanced amplifier (SLMBA). It is illustrated that, by using proper harmonic tuning in the control amplifier branch, the load trajectory of the balanced amplifier can be made close to the real axis, which is beneficial to recover peak power and efficiency at both back-off and saturation of the SLMBA in wideband operation. To validate the idea, a wideband prototype operating from 1.9 to 2.6 GHz was designed. Measured drain efficiency of 61.0% to 66.5% at peak power and 53.2% to 64.1% at 8-dB back-off are achieved. When driven with a 60-MHz long-term evolution signal with an 8-dB peak-to average power ratio, the proposed SLMBA achieves over 52% average drain efficiency, and better than −45-dBc adjacent channel power ratio with digital predistortion.