A Theoretical Method to Optimize the Control Signal Power for High-Efficiency Symmetrical Load Modulated Balanced Amplifier Designs

The novelty of this letter is proposing a theoretical method to guide the optimization of the control signal power (CSP) in a symmetrical load-modulated balanced amplifier (SLMBA) design. Theoretical analysis reveals that the magnitude optimization of the CSP needs to trade off the back-off efficiency and the output back-off (OBO) range, while the phase offset of the CSP should be optimized close to 180°. To verify the proposed theoretical method, a 1.9–3.2 GHz high-efficiency SLMBA is realized. Measured results show that the SLMBA achieves the drain efficiency (DE) of 47%–65% at saturation, 40%–62% at 6 dB back-off, and 42%–60% at 10 dB back-off, respectively. Tested by a 20 MHz 5G New Radio (NR) signal with use of digital predistortion (DPD), the adjacent channel leakage ratio (ACLR) levels of the SLMBA are better than −45.5 dBc across the band.