Though Outphasing power amplifiers (OPAs) can maintain high efficiency over a large dynamic range, their bandwidth should be further extended to satisfy the wireless communication systems. This paper presents a complex combining method for designing wideband OPAs. Complex combining impedance is adopted to compensate the frequency dispersion of the active load modulation in the OPA, leading to an extended bandwidth. It is illustrated for the first time that the load modulation trajectories of the OPA can be corrected over a wide bandwidth by elaborately designing the complex combining impedance. Furthermore, a comprehensive theoretical analysis is conducted on the transmission-line based combiner to derive the complex load impedance needed at different frequency points, recovering the back-off efficiency of a broadband OPA. As a proof of concept, a broadband OPA operating over 1.7-2.2 GHz is designed and fabricated. The experimental results show the fabricated OPA delivers a maximum output power of 43.1-44.3 dBm with a drain efficiency of 63.4%-78.4%. Meanwhile, a 6-dB back-off drain efficiency of 45.5%-70.4% can also be achieved by the fabricated OPA.

Doherty power amplifier (DPA) has shown great potentials in wireless communication systems. However, the output power and efficiency of a DPA are very susceptible to load mismatch. This paper presents the load mismatch analysis and compensation of coupler-based DPAs leveraging on dual-input and mode reconfiguration techniques. A comprehensive analysis, which takes voltage clipping into consideration, is conducted on a coupler-based dual-input DPA (CBDI-DPA) under load mismatch condition. It is illustrated that the parallel Doherty mode could recover the saturation and back-off drain efficiencies (DEs) for the load mismatch in the left and right half parts of the Smith chart, respectively. And the serial Doherty mode could recover the back-off and saturation DEs for the load mismatch in the left and right half parts of the Smith chart, respectively. As a validation, a CBDI-DPA operating at 2.4 GHz is fabricated and measured in this paper. Under the optimal load impedance condition, the fabricated CBDI-DPA delivers a saturation power of more than 43.5 dBm, a saturation DE of more than 70% and a 6 dB back-off DE of more than 60% in both the parallel and the serial Doherty modes. Meanwhile, the simulation and experimental results demonstrate the proposed method can recover the output power and efficiency of a DPA when the load mismatch is inside the 2:1 VSWR circle.

With the prevalence of complex modulated signals, it is of utmost significance to research the extension of the dynamic power range of radio frequency (RF) power amplifiers (PAs). This article proposes a divisional load-modulated balanced amplifier (DLMBA) for extending the high-efficiency power range. The proposed DLMBA is composed of a local modulated Doherty PA (DPA) and a class-C biased balanced PA (BPA) pair. The output signal of the local DPA is fed into the isolation port of the output coupler of the BPA pair, forming a global load modulation. The design parameters of the DLMBA are derived after a comprehensive analysis. It is illustrated that the dynamic power range of the DLMBA can be extended beyond 12 dB by combining a local DPA and a BPA pair. Meanwhile, each subamplifier of the DLMBA is presented with a modulated impedance over the whole dynamic power range, avoiding voltage oversaturation. As a validation, a DLMBA operating over 1.85–2.05 GHz is fabricated and measured in this article. The fabricated DLMBA delivers a maximum output power of more than 44.8 dBm, a saturation drain efficiency (DE) of more than 53%, and a 13 dB back-off DE of more than 44% in the interested frequency band. Meanwhile, when the DLMBA is excited by a 20-MHz wideband signal with a peak-to-average ratio of 10.2 dB, the measured adjacent channel leakage ratio reaches $-$ 47.4 dBc after digital predistortion.

Multi-mode multi-band power amplifiers (PAs) are becoming increasingly important for wireless communication systems that need to cover multiple frequency bands. This paper presents a dual-mode dual-band Outphasing power amplifier (OPA). OPA and inverted OPA (IOPA) operation modes are enabled at two frequency bands leveraging on the periodicity of the non-commensurate transmission line combiner (NCTLC). It is illustrated that the different base and delta lengths required by the OPA and IOPA modes can be satisfied by the NCTLC at different frequency bands. To validate the proposed method, a dual-mode dual-band OPA operating over 0.89–0.93 GHz (OPA mode) and 1.89–1.96 GHz (IOPA mode) is designed and fabricated. Measurement results show the fabricated OPA achieves 6 dB back-off drain efficiencies (DEs) of 41.3%–46.2% and 50.1%–62.3% at the frequency bands of 0.89–0.93 GHz and 1.89–1.96 GHz, respectively.

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.

There are lots of works on the bandwidth extension of symmetrical Doherty power amplifier (S-DPA) with a back-off range of 6 dB. However, it is still a challenge to simultaneously extend the bandwidth and back-off range of a S-DPA. This paper proposes a design methodology for extending the back-off range of a broadband S-DPA. Nonlinear current profile is introduced into the carrier sub-amplifier of the S-DPA. In this way, unequal power will be delivered to the load by the carrier and peaking amplifiers, leading to an extended high efficiency power range. More importantly, compared with previous works, the inversion ratio of the impedance inverter after the carrier transistor will be reduced in the proposed S-DPA, increasing the operation bandwidth. The combiner parameters of the proposed S-DPA with extended back-off range are derived based on a pre-determined nonlinear current profile. It is illustrated that the combiner parameters of the S-DPA can be expressed as a function of the combining load. Then, the bandwidth of the proposed S-DPA is subsequently analyzed under different combining load conditions. As a validation, a 1.4–2.2 GHz S-DPA with extended back-off range is implemented in this paper. Under a continuous-wave (CW) signal excitation, the fabricated S-DPA achieves a maximum output power of 40.2–43 dBm, a saturation drain efficiency (DE) of 56%–74% and a 9.0 dB back-off DE of 45%–52.5% over 1.4–2.2 GHz. Moreover, the fabricated S-DPA is also measured by the excitation of 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 S-DPA changes from $-$ 30.7 dBc to $-$ 21.1 dBc at the lower band and from $-$ 31.9 to $-$ 21.1 dBc at the upper band over 1.4–2.2 GHz when the average output power is 33.0 dBm.