Based on large-signal simulations, this article proposes a simplified method to emulate the active load modulation between the carrier and peaking transistors in a Doherty power amplifier (DPA) ...design. In contrast to the conventional load-pull method, the proposed method contributes to emulating the active load modulation between the load-modulated transistors with considering their nonlinear interaction. It offers the advantages of predicting the real-world performance of the load-modulated transistors and providing the optimum load-modulation trajectories to be synthesized in a DPA design. To verify the proposed method, a two-way millimeter-wave (mmWave) gallium nitride (GaN) microwave monolithic integrated circuit (MMIC) DPA is designed from 25.5 to 27 GHz. The measured results show that the realized MMIC DPA achieves power-added efficiency (PAE) higher than 30% at saturation, 27% at 6-dB back-off, and 21.5% at 8-dB back-off, with a saturated output power higher than 31.4 dBm across the band. When tested using a 400-MHz modulated signal with digital predistortion (DPD), the MMIC DPA shows adjacent channel power ratio (ACPR) levels better than <inline-formula> <tex-math notation="LaTeX">-</tex-math> </inline-formula>40 dBc over the band.
This paper proposes a multiobjective Bayesian optimization strategy to deal with the complex matching problem of designing a broadband 20-W gallium nitride Doherty power amplifier (DPA). Applying the ...proposed method, the DPA's matching networks are optimized to align the desired and the realized impedance trajectories both at saturation and power backoff from 1.5 to 2.4 GHz. By combining a programming environment with the commercial electronic design automation (EDA) software, the optimization process is implemented automatically. Comparison designs reveal that the proposed method outperforms the built-in optimizer of the commercial EDA software for broadband DPA designs. When tested with a single-carrier 20 MHz long-term evolution signal, the measured results show that the DPA achieves an average efficiency of 45.3%-53.6% at 7 dB backoff across the band, with the adjacent channel power ratio levels better than -45.6 dBc after using digital predistortion.
We present a general analytical solution for the active input impedances of a given <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>-port impedance network as a function of ...the loading of its ports by either active or passive devices. To demonstrate the simplicity and ease of use of our approach, we derive the input impedance equations of a conventional balanced power amplifier (BPA) and the load-modulated balanced amplifier (LMBA) and the effects of mismatching the output load. We next focus on the properties of the hybrid coupler and present a general heuristic of categorization, as well as the identification of a missing topology. This missing topology is what we refer to as the load-modulated linearizer (LML), which utilizes active load-modulation to absorb individual out-of-band (OOB) amplitude to amplitude (AM/AM) intermodulation distortion (IMD) components at the output of a power amplifier (PA). When properly designed, the LML requires only slightly more additional power than the IMD power it absorbs, making it very efficient. It retains the power conservation properties of the LMBA and achieves better linearization than an equivalent digital predistortion (DPD) system, at a very low power and complexity penalty. As the LML operates at the output of the nonlinear PA, it can independently target individual IMD tones without affecting the rest.
A complete theoretical analysis is presented for a highly efficient power amplifier (PA) architecture based on a non-reciprocal combiner. The architecture consists of two amplifier branches and a ...microwave circulator acting as the output combiner, referred to as the circulator load-modulated amplifier (CLMA). The continuous-mode (CM) design technique has been further exploited for the CLMA to demonstrate the wideband capabilities of the architecture. The analysis reveals that the CLMA performs active load modulation to maintain high PA efficiency performance across a wide bandwidth and large output power dynamic range. As a proof of concept, a CLMA demonstrator circuit based on gallium nitride (GaN) transistors and a microwave circulator, is designed and characterized with continuous-wave and modulated-signal measurements. The implemented CLMA prototype circuit experimentally demonstrates Doherty-like efficiency enhancement over a large bandwidth covering 2.1 to 3.5 GHz. In measurements, the prototype exhibits a drain efficiency of 46.7-57.5% at peak output power and 35.6-50.6% at 7-dB output power back-off level, within the design bandwidth. When tested with a 60-MHz multi-carrier orthogonal frequency-division multiplexing (OFDM) signal having a 7-dB peak-to-average power ratio (PAPR), an average efficiency of 48.5% with better than <inline-formula> <tex-math notation="LaTeX">-</tex-math> </inline-formula>47.5-dBc adjacent channel leakage ratio (ACLR) is achieved after applying digital pre-distortion (DPD).
The paper covers one of the communication technologies used in wireless sensor networks. We have presented improvements in existing radio frequency identification (RFID) systems to address the ...problem of the phase selection in active load modulation (ALM). The phase selection affects the interoperability of communication devices and has to be addressed in the design phase of a new tag. A novel transmission method is presented to make the phase selection irrelevant for device interoperability. A second solution is shown to improve the existing system synchronization, which allows operation with arbitrary selected phase. A mathematical analysis of signals present on the antenna was used together with the reference reader model to perform an analysis of proposed improvements. We proved that the proposed transmission method is less affected by phase selection. Furthermore, we demonstrated that existing system improvement allows synchronization and operation at an arbitrarily selected phase despite the continuous transmission and large signal-to-interference ratio.
There is an impedance conflict between the fundamental harmonic of f 2 and the second of f 1 if f 2 = 2f 1 . In this brief, a methodology employing the harmonic active load modulation (HALM) ...technique is utilized for solving this problem. A main power amplifier and an active load modulator constitute the overall circuit. This technique transforms the second harmonic load impedance to the optimum by injecting second harmonic power in the lower band. In order to improve the overall efficiency, a method of searching optimal location parameter is proposed to achieve the minimum extra power in harmonic injection. A power amplifier (PA) working at 1.7 and 3.4 GHz is fabricated for validation. At 1.7 GHz, the HALM technique brings an improvement of 14% in overall efficiency and an increase of 0.7 dB in output power. As for 3.4 GHz, the fabricated PA delivers overall efficiency of 78.5% and output power of 41.3 dBm without HALM.
This letter presents a new antenna topology to implement the load modulation in the Doherty transmitter, which resulted in enhancing the bandwidth compared to previous works. The active load ...modulation is realized by using a monopole array antenna, which serves as both Doherty combiner and wave radiator. The load impedances of amplifiers can be dynamically tuned through the mutual coupling of the array elements. Detailed design equations and procedures are developed. For verification, a Doherty transmitter operating at 1.95-2.10 GHz has been designed and fabricated using GaN HEMT transistors. The prototype transmitter exhibited a power-added efficiency of 53% at peak power level and maintained an efficiency of 43% at 6.8-dB backoff, over the frequency band of 1.95-2.10 GHz.
Active load modulation and harmonic injection can be used to boost the power amplifier's (PA) efficiency, but these techniques must add a fundamental external source or a harmonic generator. In this ...paper, a two‐way power amplifier architecture is introduced to extend high‐efficiency operation bandwidth by utilizing concurrent active load modulation with a waveform mapping method. Active load modulation is realized in between the two branches with the aid of independent input amplitude and phase control. Based on a calculated waveform database, high‐efficiency operations for both transistors from 1 to 4 GHz are designed in a self‐defined optimization platform considering waveform distance and input parameters. Finally, this PA is fabricated and measured to offer 41.6 to 45.0 dBm power, 8.2 to 11.7 dB gain, and 56% to 89% drain efficiency from 0.85 to 3.85 GHz.
The conventional Doherty output combiner limits the bandwidth of operation in the asymmetric Doherty power amplifiers (DPAs). In this study, an output combiner that is designed using a harmonic-tuned ...continuum mode active load modulation technique is proposed with the main target of extending the bandwidth of operation in the asymmetric DPAs. Through this methodology, design equations are derived and multiple harmonic impedance solutions are provided. This offers greater freedom for designing the output combiner of the asymmetric DPA which consists of the impedance inverting network and the impedance transforming network. Moreover, enhancements in the efficiencies at back-off and saturation power levels are made possible. The efficacy of the design strategy is demonstrated by the realised broadband asymmetric DPA prototype working within the band of 1.4–2.45 GHz. The experimental results have shown 54.55% bandwidth of operation, accounting for about 0.95–12.55% increment in bandwidth as compared with some recently published DPAs in the literature. Substantially, drain efficiencies within 35.5–52% at 6 dB output power back-off level and 47.5–64.2% at peaking power level are also recorded from the experiments. The maximum output power and gain are recorded at 43.52 dBm and 13.03 dB, respectively.
A proposed method for achieving active load-modulation technique without using a quarter-wavelength transmission line is discussed and evaluated. The theoretical analysis shows that the active ...load-modulation can be achieved without using a quarter-wavelength line, where the main amplifier sees a low impedance when the input signal level is low, and this impedance increases in proportion to the amount of current contributed from the peaking amplifier. The peaking amplifier sees an impedance decreasing from infinity to the normalized impedance. To validate the method, a circuit was designed, simulated and fabricated using two symmetrical gallium nitride (GaN) transistors (6 W) to achieve a peak power of 12 W and 6 dB output back-off efficiency. The design operates with 400 MHz bandwidth at 3.6 GHz and showed an average efficiency of 50% at 6 dB back-off and an efficiency of 75% at peak power. The designed circuit was tested with CW and modulated signals, the amplifier showed an Adjacent Channel Power Ratio (ACPR) of 31–35.5 dB when tested with a wideband code division multiple access signal of 6 dB peak-average-power ratio (PAPR) at 35.5 dBm average power. Additional 20 dB of linearity improvement was achieved after adding a lineariser.
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