Design of Broadband Divisional Load-Modulated Balanced Amplifier With Extended Dynamic Power Range

Though load-modulated power amplifier (PA) has achieved great commercial success, it is still a challenge to simultaneously improve its operation bandwidth, conversion efficiency, and dynamic range. This article presents a broadband divisional load-modulated balanced amplifier (DLMBA) with enhanced efficiency at deep output back-off (OBO) power level. Broadband impedance transformers (ITs) are adopted by the sub-amplifiers in the DLMBA to ensure optimal load modulation over a wide bandwidth. The design parameters of the broadband DLMBA are derived after a comprehensive analysis. It is illustrated in this work that the proposed DLMBA can obtain wide operation bandwidth, high conversion efficiency, and extended dynamic range simultaneously. As a validation, a 1.55–2.3 GHz DLMBA is fabricated and measured in this article. Under a continuous-wave (CW) signal excitation, the fabricated DLMBA achieves a maximum output power of 44.8–45.6 dBm, a saturation drain efficiency (DE) of 54%–72%, and a 13 dB back-off DE of 48%–54% over 1.55–2.3 GHz. Moreover, the fabricated DLMBA is also measured using a 20 MHz modulated signal with a peak-to-average power ratio (PAPR) of 8.0 dB. The measured adjacent channel leakage ratios (ACLRs) of the fabricated DLMBA change from $-$ 28.3 to $-$ 25.6 dBc at the lower band and from $-$ 28.4 to $-$ 25.4 dBc at the upper band over 1.55–2.3 GHz when the average output power is 36.0 dBm.