An analytic theory for dual-input outphasing power amplifiers that incorporate in one unified treatment, the continuum of solutions for power combining including the Doherty and Chireix modes is presented. This unified theory developed at the current-source reference planes reveals the performance trade-off achieved by all of the possible power amplifier (PA) combiners within the continuum of solutions. Furthermore, it identifies a novel type of dual-input hybrid Chireix-Doherty PA that combines key features of the Doherty and Chireix operations such that the fundamental drain voltages applied to both the main and auxiliary transistors remain constant. This hybrid PA relies on an input outphasing angle varying with the input power level to obtain the correct load modulation behavior. A 2-GHz dual-input hybrid Chireix-Doherty PA is implemented using nonlinear embedding and experimentally evaluated to validate the theory. A drain efficiency of 61% at 9-dB backoff power and a maximum output power of about 43 dBm are obtained for continuous-wave (CW) measurements. The efficiency increases monotonously with output power unlike that of the Doherty PA used for comparison. When excited with a 20-MHz LTE signal with 9.5-dB peak-to-average power ratio (PAPR), the dual-input PA yields a 60.0% average drain efficiency and -48.1-dBc adjacent-channel power-leakage ratio (ACLR) after linearization.

A new type of wideband dual-input hybrid Doherty outphasing power amplifier (HDO-PA) is developed in which the load-modulation scheme continuously converts as the frequency increase, from the previously reported HDO-PA mode with maximum flat efficiency response versus power to the conventional Doherty PA mode. For a symmetric HDO-PA implementation, this corresponds to the peak-to-backoff fundamental voltage ratio of the auxiliary amplifier linearly varying from 9/7 to 2 with frequency. A transmission-line-based wideband HDO-PA prototype is first established at the current-source reference planes to cover the frequency band from 1.4-GHz to 2.5-GHz. The wideband HDO-PA is implemented next at the package reference planes by synthesizing the wideband combiner circuit required to sustain the intrinsic load-modulation behavior across the entire frequency bandwidth. A 1.4-GHz to 2.5-GHz wideband HDO-PA is fabricated and characterized using both continuous-wave and modulated signals. The 6-dB backoff efficiency varies from 60% to 44% and the maximum power from 44.8 dBm to 42.9 dBm as the frequency increases. When the PA is excited with a 20 MHz bandwidth long-term evolution signal at 1.7 GHz with 6.5 dB peak-to-average-power ratio (PAPR), the PA achieves an average drain efficiency of 50.3% with -32.0 dBc adjacent-channel-power leakage ratio (ACLR) and an average drain efficiency of 47.8% with -54.0 dBc ACLR after digital predistortion linearization.

This article presents the architecture and design methodology for a new type of dual-band Doherty power amplifier (DB-DPA), referred to as 3-Way DB-DPA, which consists of a main amplifier for each band and an auxiliary amplifier handling both bands. The 3-Way DB-DPA improves the average drain efficiency in concurrent dual-band operation compared to the traditional 2-Way DB-DPA, by avoiding early clipping in the main amplifiers, while benefiting from load—pulling from the auxiliary power amplifier (PA). This improvement is verified in theory and simulation at the current-source reference planes and in measurement with a fabricated 1.5- and 2-GHz dual-band PA. A statistical analysis using 2-D continuous-wave (CW) signals with long-term evolution (LTE) probability distribution functions (PDFs) is performed and demonstrated an improvement in the concurrent average efficiency by 15 percentage points compared to the conventional 2-Way DB-DPA. In nonconcurrent operation, the measured CW drain efficiency in the lower band (1.5 GHz) is 82.8% at peak and 66.6% at 9.6-dB backoff, and the measured CW drain efficiency in the upper band (2.0 GHz) is 70.0% at peak and 48.4% at 9.4-dB backoff. The CW concurrent-balanced drain efficiency reaches 66.2/52.0% in the 3-Way DB-DPA at 3-/6-dB backoff. In single-band operation at 1.5/2.0 GHz, the average power and average drain efficiency after linearization by digital predistortion (DPD) are 35.1/37.4 dBm and 65.0/53.7%, respectively, for an LTE signal with 10-MHz bandwidth and 6.1-dB peak-to-average power ratio (PAPR). In concurrent operation, the 3-Way DB-DPA is driven by two 10-MHz LTE uncorrelated signals at 1.5 GHz with 6.86-dB PAPR and at 2.0 GHz with 6.26-dB PAPR, and the average total power and average concurrent drain efficiency after DPD are 37.5 dBm and 54.24%, respectively.

A novel frequency-agile power amplifier (PA) designed with a modified class-J theory enforcing constant maximum and minimum instantaneous drain voltages for all frequencies is presented. The resulting high-efficiency class-J mode that requires a reconfigurable drain supply exhibits clockwise fundamental- and second-harmonic load impedance trajectories versus frequency facilitating the PA design. This clockwise-loaded class-J (CLCJ) mode enables frequency-agile capability with enhanced efficiency when the proper drain supply voltage codesigned with the clockwise fundamental and harmonic loads is applied. The CLCJ PA designed from 0.8 to 2.4 GHz exhibits the measured drain efficiency in 57%-78% and 61%-86% ranges when operated in low and high compressions, respectively. To validate the frequency agility, 3G (2.84 MHz), 4G (20 MHz), and 5G (100 MHz) modulated signals were measured at different operating frequencies from 0.8 to 2.4 GHz. At 2 GHz, the average drain efficiency improved from 53% to 68% for CW signals and from 56.6% to 66.3% for a frequency-modulated 30-MHz chirp radar signal with second-harmonic injection.

This work introduces a novel design theory for a single-input hybrid Doherty power amplifier (PA) inspired by the design space existing within the previously reported dual-input Doherty–Chireix (outphasing) continuum. Unlike the conventional $\lambda/4$ Doherty PA inverter which only performs the correct load modulation at its center frequency, the hybrid Doherty PA (HD $\omega$ -PA) combiner network achieves a wideband load modulation using the frequency dependence of the electrical length of the output combiner lines versus frequency for sliding the PA mode of operation. A modified theory is presented in this work to allow for a single-input PA implementation. In this new design, the outphasing angle is only changing with frequency and not the input power. A transmission line phase shifter is used to provide the correct frequency-dependent input phase offset ensuring the correct wideband load modulation performed by the output combiner. A novel methodology is also proposed to select the optimal input phase offset to reduce the variation in the saturation power versus frequency and minimize the circuit size. A proof-of-concept demonstrator PA circuit is designed to operate from 2.5 to 3.3 GHz. When the fabricated PA is excited by a 20-MHz long-term evolution (LTE) modulated signal with 6-dB peak-to-average-power ratio (PAPR), an average efficiency of 45%–59% and adjacent channel leakage ratio (ACLR) less than $-$ 50 dBc are achieved after digital predistortion (DPD) across the entire band. When the fabricated PA is excited by a 5G-like 50-MHz orthogonal frequency-division multiplexing (OFDM) signal with 10-dB PAPR, an average efficiency of 33%–41% and ACLR less than $-$ 44 dBc are achieved after DPD across the entire band.