Broadband Sequential Load-Modulated Balanced Amplifier With Source Second Harmonic Control

This letter develops an enhanced efficiency and expanding design space method for the sequential load modulated balanced amplifier (SLMBA). The nonlinear factor of the source second harmonic is introduced to extend the load impedance design space of the continuous Class-F⁻¹ control amplifier (CA), thereby further improving the efficiency and design space of CA. Based on the load modulation mechanism of SLMBA, the load impedance design space of the balanced amplifier (BA) can be extended by the nonlinear factor of the source second harmonic. Utilizing this method, the SLMBA can achieve broadband and high-efficiency performance. To verify the proposed method, an SLMBA is designed and fabricated with commercial GaN transistors. The SLMBA operates in the frequency range from 1.8 to 2.6 GHz. At the designed frequency band, the drain efficiency (DE) is 57%–76% at saturation and 52.3%–62.6%/46.1%–61.4% at 6/8-dB output back-off (OBO).